Linear 5V reg with adj.current limit

[TTman]

Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
Does it exist ?

[John Fields]

On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
wrote:

>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>Does it exist ?

---
Input voltage range?

--
JF

[TTman]

"John Fields" <jfi...@austininstruments.com> wrote in message
news:gnkdn7lcl62q5qmk8...@4ax.com...

Oooops 12V fixed.

[Spehro Pefhany]

Most of the ones that use external pass transistors also have an
external resistor to set the current limit, but it's not very
accurately controlled.

Eg. MIC5156YM

Current limit 35 +/- 7 mV, so if you used a 0.35 ohm resistor, it
would limit between 80mA and 120mA at Tj = 25°C, and would change
quite a bit with junction temperature as well.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

[Rich Webb]

On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
wrote:

>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>Does it exist ?

An LM723 with a pass transistor. I've found it in lots of benchtop
supplies with adjustable voltage and current limits. The datasheet has
examples for a starting point.

--
Rich Webb Norfolk, VA

[Tim Wescott]

But the current limit voltage is the BE turn-on voltage of a transistor,
and so varies dramatically over temperature (this is what Spehro was
alluding to).

I'm not sure if the best way to do this isn't to build it up from op-amps
and a pass transistor, at least if you want a precise and stable current
limit as well as a precise and stable voltage set point.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

[John Larkin]

On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
wrote:

>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>Does it exist ?
>

The world really needs programmable current limiters and
current-limit-programmable voltage regulators. It's amazing how few
there are. The current limiters are mostly fixed-function stuff, like
for USB or PoE.

You could make it yourself, but it would take a bunch of parts.


--

John Larkin, President Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

[Phil Hobbs]

Tim Wescott wrote:
>
> On Sat, 31 Mar 2012 09:35:44 -0400, Rich Webb wrote:
>
> > On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
> > wrote:
> >
> >>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up
> >>... Does it exist ?
> >
> > An LM723 with a pass transistor. I've found it in lots of benchtop
> > supplies with adjustable voltage and current limits. The datasheet has
> > examples for a starting point.
>
> But the current limit voltage is the BE turn-on voltage of a transistor,
> and so varies dramatically over temperature (this is what Spehro was
> alluding to).
>
> I'm not sure if the best way to do this isn't to build it up from op-amps
> and a pass transistor, at least if you want a precise and stable current
> limit as well as a precise and stable voltage set point.
>

If there's a negative supply handy, an LM317 is a good fit--use an OC
comparator like an LM393 or 319 to pull the adjust pin down to -1.2V.
(To the OP: Watch that the output cap doesn't blow up the regulator when
you do this.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

[Jim Thompson]

On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
wrote:

>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>Does it exist ?
>

Here might be a starting place, with adjustable voltage output voltage
_and_ current limit....

http://www.analog-innovations.com/SED/ConceptualLabSupply.pdf

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

[Joerg]

Bingo!

That's the way it's done. Lots of linear "bricks" still use that old
723. Comes under other prefixes as well, such as uA723. It is one of
those "forever chips".

--
Regards, Joerg

http://www.analogconsultants.com/

[whit3rd]

On Saturday, March 31, 2012 1:17:33 AM UTC-7, TTman wrote:
> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
> Does it exist ?

Yes, of course, there's the uA723 and its clones. More modern, one
can use an LP2951. The onsemi.com datasheet, figure 26, shows
a suitable configuration with three external transistors.

It's not easy to put current-sense resistors, high current pass transistors,
and accurate reference voltages on a chip with op amps. So,
the choices are limited, and it's not usually a one-chip design.

How much accuracy do you really need? If the
output has to be 12.0 +/- 0.1 V, and current minimum
has to be 100 +/- 1 mA, there have to be some accurate
op amps for the voltage and current sensing, in addition to
a good trimmed voltage reference. Two chips and a pass
transistor, minimum. In the old days, there were lots of
four-terminal regulators (easier to add pass transistor and
a current sense resistor); I miss those. uA78G was a dandy
building block.

[John Larkin]

On Sat, 31 Mar 2012 10:11:05 -0700, Joerg <inv...@invalid.invalid>
wrote:

I designed a power supply recently, and was surprised that nothing
better than a 723 was available.

[Joerg]

John Larkin wrote:
> On Sat, 31 Mar 2012 10:11:05 -0700, Joerg <inv...@invalid.invalid>
> wrote:
>
>> Rich Webb wrote:
>>> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
>>> wrote:
>>>
>>>> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>>>> Does it exist ?
>>> An LM723 with a pass transistor. I've found it in lots of benchtop
>>> supplies with adjustable voltage and current limits. The datasheet has
>>> examples for a starting point.
>>>
>> Bingo!
>>
>> That's the way it's done. Lots of linear "bricks" still use that old
>> 723. Comes under other prefixes as well, such as uA723. It is one of
>> those "forever chips".
>
> I designed a power supply recently, and was surprised that nothing
> better than a 723 was available.
>

Yes, it's like the Willys Jeep and the Land Rover. Modern linear
regulators are often ill-conceived in that they do not allow access to
internal stuff like switcher chips do.

You could roll your own using a Cypress PSoC. They have analog building
blocks in there and AFAIK are the only affordable analog programmable
device out there. It's not against the law to abandon the digital stuff
in them but they do cost around a buck or more, which is a problem for
many of my cases. The performance of the analog parts is not much to
write home about but one can play tricks like automatic offset
compensation because the uC in there is now essentially free. Once
you've got a design going you could file it away as in-house IP and use
it over and over again.

[John Larkin]

On Sat, 31 Mar 2012 12:53:00 -0700, Joerg <inv...@invalid.invalid>
wrote:

The problem with "modern" parts like that is (1) all the work you have
to do to program them and (2) they only work at low voltages and (3)
they will be obsolete before the 723 is!

[Joerg]

Which is why I like the 723 :-)

Plus nothing can beat the 17c price tag:

http://avnetexpress.avnet.com/store/em/EMController/_/A-1413265/An-0?action=part&catalogId=500201&langId=-1&storeId=500201&CMP=KNC-Supplyframe_VSE-T11

[Jamie]

Phil Hobbs wrote:
> Tim Wescott wrote:
>
>>On Sat, 31 Mar 2012 09:35:44 -0400, Rich Webb wrote:
>>
>>
>>>On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
>>>wrote:
>>>
>>>
>>>>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up
>>>>... Does it exist ?
>>>
>>>An LM723 with a pass transistor. I've found it in lots of benchtop
>>>supplies with adjustable voltage and current limits. The datasheet has
>>>examples for a starting point.
>>
>>But the current limit voltage is the BE turn-on voltage of a transistor,
>>and so varies dramatically over temperature (this is what Spehro was
>>alluding to).
>>
>>I'm not sure if the best way to do this isn't to build it up from op-amps
>>and a pass transistor, at least if you want a precise and stable current
>>limit as well as a precise and stable voltage set point.
>>
>
>
> If there's a negative supply handy, an LM317 is a good fit--use an OC
> comparator like an LM393 or 319 to pull the adjust pin down to -1.2V.
> (To the OP: Watch that the output cap doesn't blow up the regulator when
> you do this.)
>
> Cheers
>
> Phil Hobbs
>

you can use the diode trick to lift the common :)

Jamie

[Tim Wescott]

But if I were tasked with designing a linear supply that had accurate
current limiting over any real temperature range, I would not use the
723's current limit input, for the reasons already cited.

Putting that aside (and it is a quibble, unless you have some need of
accurate current limiting), it's still a nice chip.

[Joerg]

Tim Wescott wrote:
> On Sat, 31 Mar 2012 10:11:05 -0700, Joerg wrote:
>
>> Rich Webb wrote:
>>> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
>>> wrote:
>>>
>>>> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up
>>>> ... Does it exist ?
>>> An LM723 with a pass transistor. I've found it in lots of benchtop
>>> supplies with adjustable voltage and current limits. The datasheet has
>>> examples for a starting point.
>>>
>>>
>> Bingo!
>>
>> That's the way it's done. Lots of linear "bricks" still use that old
>> 723. Comes under other prefixes as well, such as uA723. It is one of
>> those "forever chips".
>
> But if I were tasked with designing a linear supply that had accurate
> current limiting over any real temperature range, I would not use the
> 723's current limit input, for the reasons already cited.
>

Yeah, it sure ain't a precision circuit and compensating for the Vbe
tempco would be a bear. I wish they had put a 2nd error amp in there
like the TL494 has.

Coaxing a TL494 into linear mode mode via a PWM trick would be cool.
Maybe run one output into an RC lowpass and drive the gate of a power
MOSFET with that. But hand out sick bags before the design review ...

> Putting that aside (and it is a quibble, unless you have some need of
> accurate current limiting), it's still a nice chip.
>

It's pretty much the only one out there, at least in the sub-20c class.

[Phil Hobbs]

Or just put two in series with the output, inside the feedback loop.
But in an off-line supply, it's usually easy to generate a low-current
negative rail, or else use an LM395 instead of the 317. (Same die,
different metallization.)

[Jasen Betts]

On 2012-03-31, TTman <pcw1...@ntlworld.com> wrote:
>
> "John Fields" <jfi...@austininstruments.com> wrote in message
> news:gnkdn7lcl62q5qmk8...@4ax.com...
>> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
>> wrote:
>>
>>>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>>>Does it exist ?
>>

>> Input voltage range?
>
> Oooops 12V fixed.

2W 1W
---[LM317]--[1R2]--[11R]-+-----[7805]--
| ^ | |
| | | |
`-------------+---' |
|
----------------------------------+-----


--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to ne...@netfront.net ---

[Jim Thompson]

On Sat, 31 Mar 2012 18:19:10 -0400, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>Jamie wrote:
>>
>> Phil Hobbs wrote:

[snip]

>> >
>> > If there's a negative supply handy, an LM317 is a good fit--use an OC
>> > comparator like an LM393 or 319 to pull the adjust pin down to -1.2V.
>> > (To the OP: Watch that the output cap doesn't blow up the regulator when
>> > you do this.)
>> >
>> > Cheers
>> >
>> > Phil Hobbs
>> >
>> you can use the diode trick to lift the common :)
>>
>> Jamie

You need to go below ground to stop it, _not_ above.

>
>Or just put two in series with the output, inside the feedback loop.

That might just work... from input, LM317 connected as current source,
value equal to current limit, followed by LM317 configured for 5V.

>But in an off-line supply, it's usually easy to generate a low-current
>negative rail, or else use an LM395 instead of the 317. (Same die,
>different metallization.)
>
>Cheers
>
>Phil Hobbs

Yep, My analysis for Integrated Circuit Engineering, 42 years ago...

http://www.analog-innovations.com/SED/ICE-LM195-LM117.pdf

[Spehro Pefhany]

Not sure about that- appears to be down to a single source (TI)- ST,
Fairchild and Philips seem to have all obsoleted it, (and NS is part
of TI now, of course). I'm sure onesey-twosey will be available for as
long as I care about though (at a price).

LM78x05, LM317 are good for the forseeable future.

[Joerg]

Spehro Pefhany wrote:
> On Sat, 31 Mar 2012 10:11:05 -0700, the renowned Joerg
> <inv...@invalid.invalid> wrote:
>
>> Rich Webb wrote:
>>> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
>>> wrote:
>>>
>>>> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>>>> Does it exist ?
>>> An LM723 with a pass transistor. I've found it in lots of benchtop
>>> supplies with adjustable voltage and current limits. The datasheet has
>>> examples for a starting point.
>>>
>> Bingo!
>>
>> That's the way it's done. Lots of linear "bricks" still use that old
>> 723. Comes under other prefixes as well, such as uA723. It is one of
>> those "forever chips".
>
> Not sure about that- appears to be down to a single source (TI)- ST,
> Fairchild and Philips seem to have all obsoleted it, (and NS is part
> of TI now, of course). I'm sure onesey-twosey will be available for as
> long as I care about though (at a price).
>

ON Semi has it. So does JRC, under the name NJM723. Not sure if it was
KEC (Korea) but I've seen another Asian source.

Digikey has over 10,000 from ST in stock and no obsolescence warning.
Haven't checked ST because their web site is the pits.

> LM78x05, LM317 are good for the forseeable future.
>

But no adjustable current limit which is what the OP wants. If I needed
fairly precise current limit and it was all on a tight budget I'd try to
use a TL494 as a linear regulator. That thing will likely be around
until you and I can't hold a soldering iron no more.

[Phil Hobbs]

Spehro Pefhany wrote:
>
> On Sat, 31 Mar 2012 10:11:05 -0700, the renowned Joerg
> <inv...@invalid.invalid> wrote:
>
> >Rich Webb wrote:
> >> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
> >> wrote:
> >>
> >>> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
> >>> Does it exist ?
> >>
> >> An LM723 with a pass transistor. I've found it in lots of benchtop
> >> supplies with adjustable voltage and current limits. The datasheet has
> >> examples for a starting point.
> >>
> >
> >Bingo!
> >
> >That's the way it's done. Lots of linear "bricks" still use that old
> >723. Comes under other prefixes as well, such as uA723. It is one of
> >those "forever chips".
>
> Not sure about that- appears to be down to a single source (TI)- ST,
> Fairchild and Philips seem to have all obsoleted it, (and NS is part
> of TI now, of course). I'm sure onesey-twosey will be available for as
> long as I care about though (at a price).
>
> LM78x05, LM317 are good for the forseeable future.

ST is showing it in active production,
http://www.st.com/internet/analog/product/63724.jsp

[Joerg]

Phil Hobbs wrote:
> Spehro Pefhany wrote:
>> On Sat, 31 Mar 2012 10:11:05 -0700, the renowned Joerg
>> <inv...@invalid.invalid> wrote:
>>
>>> Rich Webb wrote:
>>>> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
>>>> wrote:
>>>>
>>>>> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>>>>> Does it exist ?
>>>> An LM723 with a pass transistor. I've found it in lots of benchtop
>>>> supplies with adjustable voltage and current limits. The datasheet has
>>>> examples for a starting point.
>>>>
>>> Bingo!
>>>
>>> That's the way it's done. Lots of linear "bricks" still use that old
>>> 723. Comes under other prefixes as well, such as uA723. It is one of
>>> those "forever chips".
>> Not sure about that- appears to be down to a single source (TI)- ST,
>> Fairchild and Philips seem to have all obsoleted it, (and NS is part
>> of TI now, of course). I'm sure onesey-twosey will be available for as
>> long as I care about though (at a price).
>>
>> LM78x05, LM317 are good for the forseeable future.
>
> ST is showing it in active production,
> http://www.st.com/internet/analog/product/63724.jsp
>

Companies such as PowerOne are buying those things by the bucket. I have
yet to see an OEM linear brick supply that does not have a 723 in there.

[Phil Hobbs]

Considering that they work okay, and cost 16 cents in quantity 1, I'm
not surprised.

[Spehro Pefhany]

Oops, must have hit on a non-RoHS version or something. That's good!

I have not seen Chinese clones as with some more modern parts, but
then I have not really been looking.

[bloggs.fred...@gmail.com]

On Saturday, March 31, 2012 4:17:33 AM UTC-4, TTman wrote:
> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
> Does it exist ?

STMicro still has the L200 http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000053.pdf . Initial accuracy on the current limit is in the under 15% range but, , it can be linearized, and the tempco is very good at 0.03%/oC, no small feat for an IC that takes a lot of heat. It more than handles the power and voltages of real loads.

[Spehro Pefhany]

On Sat, 31 Mar 2012 17:12:53 -0700, the renowned Joerg

Sure, that's got to big one... any idea how many of the old-style
linear supplies they make a year? Looks like the design has not
changed since the 1970s.

[mike]

On 3/31/2012 3:54 PM, Jasen Betts wrote:
> On 2012-03-31, TTman<pcw1...@ntlworld.com> wrote:
>>
>> "John Fields"<jfi...@austininstruments.com> wrote in message
>> news:gnkdn7lcl62q5qmk8...@4ax.com...
>>> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman"<pcw1...@ntlworld.com>
>>> wrote:
>>>
>>>> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>>>> Does it exist ?
>>>
>>> Input voltage range?
>>
>> Oooops 12V fixed.
>
> 2W 1W
> ---[LM317]--[1R2]--[11R]-+-----[7805]--
> | ^ | |
> | | | |
> `-------------+---' |
> |
> ----------------------------------+-----
>
>

putting the entire output current thru the pot wiper is troubling.

[Phil Hobbs]

Not as troubling as the blue smoke and Joergish noises coming from the
resistor element when it's set below about 1/4 scale. ;)

[Jim Thompson]

On Sat, 31 Mar 2012 22:25:39 -0400, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>mike wrote:
>>
>> On 3/31/2012 3:54 PM, Jasen Betts wrote:
>> > On 2012-03-31, TTman<pcw1...@ntlworld.com> wrote:
>> >>
>> >> "John Fields"<jfi...@austininstruments.com> wrote in message
>> >> news:gnkdn7lcl62q5qmk8...@4ax.com...
>> >>> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman"<pcw1...@ntlworld.com>
>> >>> wrote:
>> >>>
>> >>>> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>> >>>> Does it exist ?
>> >>>
>> >>> Input voltage range?
>> >>
>> >> Oooops 12V fixed.
>> >
>> > 2W 1W
>> > ---[LM317]--[1R2]--[11R]-+-----[7805]--
>> > | ^ | |
>> > | | | |
>> > `-------------+---' |
>> > |
>> > ----------------------------------+-----
>> >
>> >
>> putting the entire output current thru the pot wiper is troubling.
>
>Not as troubling as the blue smoke and Joergish noises coming from the
>resistor element when it's set below about 1/4 scale. ;)
>
>Cheers
>
>Phil Hobbs

As well as undefined bias state, and noise from bouncing in and out of
"drop-out". Interesting problem... how do you do that with stability
and predictability?

[Michael A. Terrell]

Jasen Betts wrote:
>
> On 2012-03-31, TTman <pcw1...@ntlworld.com> wrote:
> >
> > "John Fields" <jfi...@austininstruments.com> wrote in message
> > news:gnkdn7lcl62q5qmk8...@4ax.com...
> >> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
> >> wrote:
> >>
> >>>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
> >>>Does it exist ?
> >>
> >> Input voltage range?
> >
> > Oooops 12V fixed.
>
> 2W 1W
> ---[LM317]--[1R2]--[11R]-+-----[7805]--
> | ^ | |
> | | | |
> `-------------+---' |
> |
> ----------------------------------+-----

Does that mess come with a fire extinguisher?


--
You can't have a sense of humor, if you have no sense.

[miso]

On 3/31/2012 9:35 AM, John Larkin wrote:
> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman"<pcw1...@ntlworld.com>
> wrote:
>
>> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>> Does it exist ?
>>
>

> The world really needs programmable current limiters and
> current-limit-programmable voltage regulators. It's amazing how few
> there are. The current limiters are mostly fixed-function stuff, like
> for USB or PoE.
>
> You could make it yourself, but it would take a bunch of parts.
>
>

Most use current limiting just for protection. It doesn't have to be
"that" accurate. Remember, it is yet another control loop. Less is more!

Funny thing is with TI buying up companies, there are less choices in
regulators. They have Unitrode and National. Maybe I left one out.

Oh yeah, 723, good stuff.

[TTman]

>
>
>> LM78x05, LM317 are good for the forseeable future.
>>
>
> But no adjustable current limit which is what the OP wants. If I needed
> fairly precise current limit and it was all on a tight budget I'd try to
> use a TL494 as a linear regulator. That thing will likely be around
> until you and I can't hold a soldering iron no more.
>
> --
> Regards, Joerg
>
> http://www.analogconsultants.com/

Thanks for all the replies.... I didn't quite express myself correctly.... I
should have said 'selectable' as opposed to 'adjustable'.
The adjustable solutions require too much effort ( for these simple test box
setups).
The optimum was mentioned by a few and thanks- I'll go with the 317
(actually 1117DT) and current limit resistor with adequate wattage for each
solution. The pot idea was good but would need a 2W+ pot lol.
My favourite 5V reg is the LM2940..
The reason for current limiting is to prevent 'smokers' if there is a short
on the UUT.... due to piss poor inspection :)

[Jamie]

And one must remember if using a rotary switch to select in/out
resistors the network should be in series, connected between each pole
so that when the pole contact leaves the nest as it's moving on towards
a new home, you don't get a totally open circuit.

Jamie

[Spehro Pefhany]

On Sat, 31 Mar 2012 22:40:31 -0700, the renowned miso <mi...@sushi.com>
wrote:

Power Trends, maybe Benchmarq if you count them.

>Oh yeah, 723, good stuff.

[Joerg]

No idea, but considering that Digikey carries over 500 just of this
model in stock means it must be selling at a pretty good clip:

http://search.digikey.com/us/en/products/HB12-1.7-AG/179-2311-ND/1634203

I never had a leadtime on any, and I or my clients have bought lots of
different voltage versions. They are very convenient for test gear
because you don't have to worry about noise. Plus it's almost guaranteed
to contain the old 723 so it's very stable. Meaning no worries about an
iffy load or instability during brown-outs.

[Jim Thompson]

Michael, On paper, it works. However, how that LM317 "floats" is
indeterminate. Possibly it just saturates up against the positive
rail until current limit is reached.

[Spehro Pefhany]

On Sun, 01 Apr 2012 08:16:19 -0700, the renowned Joerg

Yeah, I've occasionally used those in onesy-twosey, last time was a
couple months ago... didn't want to risk having to fix EMI problems
from a SMPS in a sensitive electromechanical test setup. TO-3
transistors (hermetic) even, and single-sided board. You just put them
in and they work (at least until that 85°C cap dies).

Probably lots of small volume legacy gear uses them too. Just curious
as to what that might add up to. Heck, you can still get new LM741
parts, and I bet nobody has designed that one into a new piece of
volume gear in over a decade.

[Michael A. Terrell]

Jamie wrote:
>
> And one must remember if using a rotary switch to select in/out
> resistors the network should be in series, connected between each pole
> so that when the pole contact leaves the nest as it's moving on towards
> a new home, you don't get a totally open circuit.

You need a 'Shorting Switch' that makes contact with the next
position, before breaking the existing connection. As usual, Maynard
leaves out the important detail.

[Michael A. Terrell]

Jim Thompson wrote:
>
> On Sun, 01 Apr 2012 01:31:09 -0400, "Michael A. Terrell"
> <mike.t...@earthlink.net> wrote:
>
> >
> >Jasen Betts wrote:
> >>
> >> On 2012-03-31, TTman <pcw1...@ntlworld.com> wrote:
> >> >
> >> > "John Fields" <jfi...@austininstruments.com> wrote in message
> >> > news:gnkdn7lcl62q5qmk8...@4ax.com...
> >> >> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
> >> >> wrote:
> >> >>
> >> >>>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
> >> >>>Does it exist ?
> >> >>
> >> >> Input voltage range?
> >> >
> >> > Oooops 12V fixed.
> >>
> >> 2W 1W
> >> ---[LM317]--[1R2]--[11R]-+-----[7805]--
> >> | ^ | |
> >> | | | |
> >> `-------------+---' |
> >> |
> >> ----------------------------------+-----
> >
> >
> > Does that mess come with a fire extinguisher?
>
> Michael, On paper, it works. However, how that LM317 "floats" is
> indeterminate. Possibly it just saturates up against the positive
> rail until current limit is reached.

I know that it works on paper, but to need high wattage resistors is
just poor design. That one watt pot would likely be wirewound, and very
noisy when it's adjusted.

[mike]

The devil is in the often unspecified details.
If you're only building a few and don't have to deal with component
variations
from different vendors, the job gets easier.

How many different current limits do you REALLY need?
Sounds like there's no need to switch the current limit
while attached to the DUT??
Sounds like the current limit is only approximate.
So, why the series current limting IC at all?
What's the advantage over a resistor and a 7805 equivalent?

7800s come in M and L versions with different current limits.
Might be cheaper overall to use three regulators and configure
the correct output with the wiring harness to the specific DUT.
Sometimes, there's benefit in limiting the options of the production staff.


7800s are generally stable if you let the input voltage crash into the
output voltage, but I'd check what happens with non-linear loads.

My favorite example is a USB hard drive that draws too much current
to spin up. Makes quite a racket and can't be good to have the
heads banging into the stops.

[Phil Hobbs]

An LM395 pass element, and a bit of foldback on the current limit. That
prevents the voltage and current regulation modes from fighting each
other. I sort of like the Power One approach, where the current limit
latches the output low until you turn off the supply or crank the
voltage way down and back up again. (My general purpose bench supplies
are a couple of 25-year-old Power One linears--nice and quiet, and
stable stable stable.)

[John Larkin]

On Sun, 1 Apr 2012 09:56:29 +0100, "TTman" <pcw1...@ntlworld.com>
wrote:

Polyfuses are good for fire prevention. The radial leaded ones work
well; the surface-mount ones less well.

I like to use a polyfuse and a transzorb on DC voltage inputs to my
boxes, for overvoltage/transient/reverse polarity protection.

I also have used an LM317L TO92 as a current limiter, with the adj pin
floating. It works great, but loses about 1.5 volts. I wish there was
an equivalent lower dropout on-purpose current limiter.

http://dl.dropbox.com/u/53724080/Circuits/LM317L_ilim.JPG



--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

[Phil Hobbs]

Jim Thompson wrote:
>
> On Sun, 01 Apr 2012 01:31:09 -0400, "Michael A. Terrell"
> <mike.t...@earthlink.net> wrote:
>
> >
> >Jasen Betts wrote:
> >>
> >> On 2012-03-31, TTman <pcw1...@ntlworld.com> wrote:
> >> >
> >> > "John Fields" <jfi...@austininstruments.com> wrote in message
> >> > news:gnkdn7lcl62q5qmk8...@4ax.com...
> >> >> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
> >> >> wrote:
> >> >>
> >> >>>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
> >> >>>Does it exist ?
> >> >>
> >> >> Input voltage range?
> >> >
> >> > Oooops 12V fixed.
> >>
> >> 2W 1W
> >> ---[LM317]--[1R2]--[11R]-+-----[7805]--
> >> | ^ | |
> >> | | | |
> >> `-------------+---' |
> >> |
> >> ----------------------------------+-----
> >
> >
> > Does that mess come with a fire extinguisher?
>
> Michael, On paper, it works. However, how that LM317 "floats" is
> indeterminate. Possibly it just saturates up against the positive
> rail until current limit is reached.

Yup. If the internal current limit is good enough for the purpose, you
can just leave the adjust pin open, and it works fine. The thermal
limiting gives you some slow foldback effect as well, but of course you
don't know if the limit is 1.5 A or 3.4 A, because the spec is so
sloppy.

[Phil Hobbs]

The 78Lxx parts aren't the same as the 7800s--they have far worse ripple
rejection. I gave up on them long ago. 317Ls are okay.

[Joerg]

> as to what that might add up to. ...


Multiply all the onesies and twosies times the number of Spehros,
Joergs, Johns and so on :-)

It's like Milwaukee. Hardly anyone needs more than one Sawzall but a lot
of people need one just like I do.


> ... Heck, you can still get new LM741

> parts, and I bet nobody has designed that one into a new piece of
> volume gear in over a decade.
>

I have a classic example in my portfolio. A unit that I designed in the
early 90's, still coming off a production line in Guangdong. Changes:
Zero, it's essentially still Rev A. Like with this board I always try to
design without boutique parts so unless Armageddon happens they can keep
producing it nearly forever.

[Joerg]

For bench supplies most folks want another behavior though. I sometimes
need to run mine in constant current mode and a foldback or latching
mode would nix that.

[mike]

With clean 12V going in, ripple rejection shouldn't be an issue?
Line regulation might be with a series current limit.
>
> Cheers
>
> Phil Hobbs

[SMS]

On 3/31/2012 1:17 AM, TTman wrote:
> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
> Does it exist ?

Linear, no.

I'd look at some of the USB power switches with adjustable current
limits, i.e. <http://www.micrel.com/_PDF/mic2544.pdf>. You'd need a
linear regulator in front of it though, since the input is limited to 7V.

These are very cheap.

[Jim Thompson]

On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>

wrote:

>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>Does it exist ?
>

Another way...

http://www.analog-innovations.com/SED/SimpleRegulatorWithAdjustableCurrentLimit.pdf

ILIM sets the output current limit without requiring a 2W
potentiometer.

Design of ILIM is left as an exercise for the student :-) Caution, a
negative auxiliary supply of at least -1.25V will be required to pull
output all the way to zero volts.

A similar approach should work with the two-LM317-in-series
presentation

[Jim Thompson]

On Sun, 01 Apr 2012 15:10:58 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
>wrote:
>
>>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>>Does it exist ?
>>
>
>Another way...
>
>http://www.analog-innovations.com/SED/SimpleRegulatorWithAdjustableCurrentLimit.pdf
>
>ILIM sets the output current limit without requiring a 2W
>potentiometer.
>
>Design of ILIM is left as an exercise for the student :-) Caution, a
>negative auxiliary supply of at least -1.25V will be required to pull
>output all the way to zero volts.

Or add some diodes to drop the output, then the TL431 loop.

[David Eather]

LM1086 - (I'm not sure how it goes with a floating adjust pin)


--
We have failed to address the fundamental truth that endless growth is
impossible in a finite world.

[Allan Herriman]

http://www.linear.com/product/LT3080

Please refer to the figure in the datasheet labelled "Current Source".

Important: it only gives low dropout if you have an independent bias
supply.
Dropout is about 350mV from the main input and about 1.35V from the bias
input.

See also LT3082, '3083, '3085.

Disclaimer: I haven't used these particular parts in any design.

Regards,
Allan

[Jan Panteltje]

On a sunny day (Sun, 01 Apr 2012 15:10:58 -0700) it happened Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote in
<h7khn75mgcqjrba2f...@4ax.com>:

>On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
>wrote:
>
>>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>>Does it exist ?
>>
>
>Another way...
>
>http://www.analog-innovations.com/SED/SimpleRegulatorWithAdjustableCurrentLimit.pdf
>
>ILIM sets the output current limit without requiring a 2W
>potentiometer.
>
>Design of ILIM is left as an exercise for the student :-) Caution, a
>negative auxiliary supply of at least -1.25V will be required to pull
>output all the way to zero volts.
>
>A similar approach should work with the two-LM317-in-series
>presentation
>
> ...Jim Thompson

What I do not understand is why not just put a PNP in front of a LM117,
and use the beta:

PNP <1A in out
+12 ------ e c ----------------- LM317 -------------> out
b | | | |
| === 150 [ ] | ===
470 [ ] <10mA | |--- |
| /// | ///
4k7 [ ]<-- [ ]<---
| | Imax | | Uout
/// /// /// ///


Find one with a beta > 100, normally it will be on and drop less than 300 mV,
should be on heatsink too as it will get hot if it limits.

Beta does not really change THAT much.
I have used this sort of limiter, and it works great.

[Alexander]

Am 01.04.2012 00:54, schrieb Jasen Betts:

>
> 2W 1W
> ---[LM317]--[1R2]--[11R]-+-----[7805]--
> | ^ | |
> | | | |
> `-------------+---' |
> |
> ----------------------------------+-----

One L200 from STMicroelectronics will do the same. Unfortunately it also
requires high power resistors for the current limit.

Cheers,
Alexander

[Jasen Betts]

On 2012-04-01, Jim Thompson <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
> On Sun, 01 Apr 2012 01:31:09 -0400, "Michael A. Terrell"
><mike.t...@earthlink.net> wrote:
>
>>
>>Jasen Betts wrote:
>>>
>>> On 2012-03-31, TTman <pcw1...@ntlworld.com> wrote:
>>> >
>>> > "John Fields" <jfi...@austininstruments.com> wrote in message
>>> > news:gnkdn7lcl62q5qmk8...@4ax.com...
>>> >> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>
>>> >> wrote:
>>> >>
>>> >>>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>>> >>>Does it exist ?
>>> >>
>>> >> Input voltage range?
>>> >
>>> > Oooops 12V fixed.
>>>
>>> 2W 1W
>>> ---[LM317]--[1R2]--[11R]-+-----[7805]--
>>> | ^ | |
>>> | | | |
>>> `-------------+---' |
>>> |
>>> ----------------------------------+-----
>>
>>
>> Does that mess come with a fire extinguisher?
>
> Michael, On paper, it works. However, how that LM317 "floats" is
> indeterminate. Possibly it just saturates up against the positive
> rail until current limit is reached.

I'm mistreating the pot. probably enough to destroy it, it probably
needs a 12W part instead of the 1W shown.

http://search.digikey.com/us/en/products/RES15RE/RES15RE-ND/824032
$35, suddenly a cheap design isn't.

but if (as it transpires) a switch can be used instead 100mA steps
can be done with 1/4W resistors, (after the initial 2W)

http://search.digikey.com/us/en/products/C5P0112N-A/451-1027-ND/514081
$9 switch

if your prepared to program the current limit in binary it's possibly
even cheaper, eg: some number of 12R in parallel, each is good for
100mA of headroom.

--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to ne...@netfront.net ---

[Jasen Betts]

On 2012-04-01, Michael A. Terrell <mike.t...@earthlink.net> wrote:

>> >> > Oooops 12V fixed.
>> >>
>> >> 2W 1W
>> >> ---[LM317]--[1R2]--[11R]-+-----[7805]--
>> >> | ^ | |
>> >> | | | |
>> >> `-------------+---' |
>> >> |
>> >> ----------------------------------+-----
>> >
>> >
>> > Does that mess come with a fire extinguisher?
>

> I know that it works on paper, but to need high wattage resistors is
> just poor design. That one watt pot would likely be wirewound, and very
> noisy when it's adjusted.

the brief (as I understood it) was a linear regulator with a 12V supply

every watt that's burned in a resistor isn't being used to warm the
heatsink,

use 1 to 10 12 ohm 1/4W resistors in parallel for the current selection.

[bloggs.fred...@gmail.com]

On Sunday, April 1, 2012 11:04:48 PM UTC-4, Allan Herriman wrote:
> On Sun, 01 Apr 2012 11:35:44 -0700, John Larkin wrote:
>
> > On Sun, 1 Apr 2012 09:56:29 +0100, "TTman"
>

That's a $4 part...

[bloggs.fred...@gmail.com]

The trip voltage is 0.45V, so just exactly how would that require a high power resistor? That's only 1/2W at the 1 Amp limit.

[Mark Zenier]

In article <jl6ej5$58m$1...@dont-email.me>, TTman <pcw1...@ntlworld.com> wrote:
>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>Does it exist ?

The L200 used to exist. A 5 pin TO-220. Like a 317 with a adjustable
current limit set by external components. SGS-ATES, maybe ST now.

Rather low power dissipation, so putting too many volts
in was problematic. With a higher (than a LM317) dropout
voltage, too.

Mark Zenier mze...@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)

[Joerg]

Ever heard pilots talking about their $100 hamburgers? :-)

[bloggs.fred...@gmail.com]

No wonder they're going nuts...

[bloggs.fred...@gmail.com]

On Saturday, March 31, 2012 5:50:32 AM UTC-4, TTman wrote:
> "John Fields" <jfi...@austininstruments.com> wrote in message
> news:gnkdn7lcl62q5qmk8...@4ax.com...
> > On Sat, 31 Mar 2012 09:17:33 +0100, "TTman"
>

> > wrote:
> >
> >>Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
> >>Does it exist ?
> >

> > ---
> > Input voltage range?
> >
> > --
> > JF
>
> Oooops 12V fixed.

With those kind of voltages, you could do something like this with junkbox parts. It's a simple highside current monitor driving a low RDS,ON MOSFET in foldback mode. Any 5V regulator will work. If you don't like the rheostat then replace it with a DPST to select a 10R for 100mA or a 100R for 1A trip.
Please view in a fixed-width font such as Courier.

.
.
. 0-1A ADJ FOLDBACK 5V REGULATOR
.
.
. .----------------[100K]------------------+--------.
. | | |
. | | |
. | ----------- | |
. | 5W | V.Reg | G |
. +12V >-+-/\/\/\-+--+-|IN 5V|--+-----+-- D S---+--|->OUT
. | 3.9R | | | | | | | |
. | | === -----+----- | === IRF540 | |
. [39K] | | | [39K] | | |
. | | GND GND | GND | |
. | 1N4148 | | | |
. +--|>|---|----------. +------[390]------' |
. | | | | [100]
. | [39K] +12V | | |
. | | | | LM358 | 0.1u |
. | | |\| | | .----||----+
. | +---|-\ |/ | | |
. | | | >-|PN3904 | | |\ |
. +--------|---|+/ |> +--[10K]--|--|+\ |
. | | |/| | .| | | >----'
. | | UA | +--------|--[10K]--+--|-/
. | | | | | |/
. | | | | .----+ UB
. | | | | | |_
. [39K] [39K] | [10K] | |/|
. | | | | | [100]
. | | | | | /|
. GND>--+--------+-----+----+---|----+--------------------->GND
. |
. '------------> I_TRIP 1Volt/Amp
.
. adjust with output
. terminals open
. P = 1.3 W
. FET,MAX
.
.
. P = 3.2 W
. REG,MAX
.
.
.

[Jim Thompson]

Nice simple solution ;-)

[josephkk]

On Sat, 31 Mar 2012 13:01:12 -0700, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Sat, 31 Mar 2012 12:53:00 -0700, Joerg <inv...@invalid.invalid>
>wrote:
>
>>John Larkin wrote:
>>> On Sat, 31 Mar 2012 10:11:05 -0700, Joerg <inv...@invalid.invalid>
>>> wrote:
>>>
>>>> Rich Webb wrote:
>>>>> On Sat, 31 Mar 2012 09:17:33 +0100, "TTman" <pcw1...@ntlworld.com>

>>>>> wrote:
>>>>>
>>>>>> Can anyone suggest anything ? A 1 amp device with I adj. from 100mA up ...
>>>>>> Does it exist ?

>>>>> An LM723 with a pass transistor. I've found it in lots of benchtop
>>>>> supplies with adjustable voltage and current limits. The datasheet has
>>>>> examples for a starting point.
>>>>>
>>>> Bingo!
>>>>
>>>> That's the way it's done. Lots of linear "bricks" still use that old
>>>> 723. Comes under other prefixes as well, such as uA723. It is one of
>>>> those "forever chips".
>>>

>>> I designed a power supply recently, and was surprised that nothing
>>> better than a 723 was available.
>>>
>>
>>Yes, it's like the Willys Jeep and the Land Rover. Modern linear
>>regulators are often ill-conceived in that they do not allow access to
>>internal stuff like switcher chips do.
>>
>>You could roll your own using a Cypress PSoC. They have analog building
>>blocks in there and AFAIK are the only affordable analog programmable
>>device out there. It's not against the law to abandon the digital stuff
>>in them but they do cost around a buck or more, which is a problem for
>>many of my cases. The performance of the analog parts is not much to
>>write home about but one can play tricks like automatic offset
>>compensation because the uC in there is now essentially free. Once
>>you've got a design going you could file it away as in-house IP and use
>>it over and over again.
>
>The problem with "modern" parts like that is (1) all the work you have
>to do to program them and (2) they only work at low voltages and (3)
>they will be obsolete before the 723 is!

In a way it is really cool, the 723 is older than the 555 and still known
to be very useful. Kinda like the uA741 and the LM101 as well.

?-)

[Jim Thompson]

On Thu, 05 Apr 2012 09:32:35 -0700, Fred Abse
<excret...@invalid.invalid> wrote:

>On Wed, 04 Apr 2012 19:59:58 -0700, josephkk wrote:
>
>> In a way it is really cool, the 723 is older than the 555 and still
>> known to be very useful. Kinda like the uA741 and the LM101 as well.
>

>As I've intimated before, I've had endless fun (not), getting 723s with
>added pass transistors, to stop oscillating at HF, in other people's
>(commercial) designs.
>
>The 741 used to latch up.Maybe they've cured that problem in the
>intervening years. I stopped using them as soon as I could.

The 741's that latched were bad copies... the originally published
schematic was of an early botched version, but was never changed...
quick-to-second-source loons missed it ;-)

[bloggs.fred...@gmail.com]

On Thursday, April 5, 2012 12:32:35 PM UTC-4, Fred Abse wrote:
> On Wed, 04 Apr 2012 19:59:58 -0700, josephkk wrote:
>

> > In a way it is really cool, the 723 is older than the 555 and still
> > known to be very useful. Kinda like the uA741 and the LM101 as well.
>

> As I've intimated before, I've had endless fun (not), getting 723s with
> added pass transistors, to stop oscillating at HF, in other people's
> (commercial) designs.
>
> The 741 used to latch up.Maybe they've cured that problem in the
> intervening years. I stopped using them as soon as I could.
>

> --
> "For a successful technology, reality must take precedence
> over public relations, for nature cannot be fooled."
> (Richard Feynman)

Was that added pass transistor a PNP common emitter? Same problem as with the modern LDOs, you need to know a little bit about phase compensation. There is no stability problem with NPN darlington current boost and the 723.

The 723 was a second iteration of an earlier general purpose linear regulator with a less than ideal voltage reference, the NE550, http://www.datasheetarchive.com/NE550-datasheet.html

[Joerg]

Fred Abse wrote:
> On Wed, 04 Apr 2012 19:59:58 -0700, josephkk wrote:
>

>> In a way it is really cool, the 723 is older than the 555 and still
>> known to be very useful. Kinda like the uA741 and the LM101 as well.
>

> As I've intimated before, I've had endless fun (not), getting 723s with
> added pass transistors, to stop oscillating at HF, in other people's
> (commercial) designs.
>

Commercial is not a guarantee for good designs. Often the circuit design
is ok but the layout is horrid.

I've never had even a whiff of a problem with the 723, they always worked.

> The 741 used to latch up.Maybe they've cured that problem in the
> intervening years. I stopped using them as soon as I could.
>

Back in its days discrete designs were often cheaper. So I rarely used
it and if I did need an opamp I preferred the 709. But the bulk of my
designs use the 324, it is much better.

[John Larkin]

On Thu, 05 Apr 2012 09:32:35 -0700, Fred Abse

<excret...@invalid.invalid> wrote:

>On Wed, 04 Apr 2012 19:59:58 -0700, josephkk wrote:
>

>> In a way it is really cool, the 723 is older than the 555 and still
>> known to be very useful. Kinda like the uA741 and the LM101 as well.
>

>As I've intimated before, I've had endless fun (not), getting 723s with
>added pass transistors, to stop oscillating at HF, in other people's
>(commercial) designs.
>

>The 741 used to latch up.Maybe they've cured that problem in the
>intervening years. I stopped using them as soon as I could.

741's were OK. It was the 709 that had bad latchup problems, when one
of the front-end transistors zenered. I remember, as a kid, deciding
to use 741s in systems, instead of 709s. The 741s were a lot more
expensive at the time.

I wonder what's the oldest IC still in production.


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

[Spehro Pefhany]

On Thu, 05 Apr 2012 13:11:04 -0700, the renowned John Larkin
<jla...@highlandtechnology.com> wrote:

>On Thu, 05 Apr 2012 09:32:35 -0700, Fred Abse
><excret...@invalid.invalid> wrote:
>
>>On Wed, 04 Apr 2012 19:59:58 -0700, josephkk wrote:
>>
>>> In a way it is really cool, the 723 is older than the 555 and still
>>> known to be very useful. Kinda like the uA741 and the LM101 as well.
>>
>>As I've intimated before, I've had endless fun (not), getting 723s with
>>added pass transistors, to stop oscillating at HF, in other people's
>>(commercial) designs.
>>
>>The 741 used to latch up.Maybe they've cured that problem in the
>>intervening years. I stopped using them as soon as I could.
>
>741's were OK. It was the 709 that had bad latchup problems, when one
>of the front-end transistors zenered. I remember, as a kid, deciding
>to use 741s in systems, instead of 709s. The 741s were a lot more
>expensive at the time.
>
>I wonder what's the oldest IC still in production.

Maybe the SN5400/7400 (ca. 1965)- still shows as "active" on TI's
website.

That's approaching the half-century mark, and starting only a few
years after ICs were first commercialized.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
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[Joerg]

John Larkin wrote:
> On Thu, 05 Apr 2012 09:32:35 -0700, Fred Abse
> <excret...@invalid.invalid> wrote:
>
>> On Wed, 04 Apr 2012 19:59:58 -0700, josephkk wrote:
>>
>>> In a way it is really cool, the 723 is older than the 555 and still
>>> known to be very useful. Kinda like the uA741 and the LM101 as well.
>> As I've intimated before, I've had endless fun (not), getting 723s with
>> added pass transistors, to stop oscillating at HF, in other people's
>> (commercial) designs.
>>
>> The 741 used to latch up.Maybe they've cured that problem in the
>> intervening years. I stopped using them as soon as I could.
>
> 741's were OK. It was the 709 that had bad latchup problems, when one
> of the front-end transistors zenered. I remember, as a kid, deciding
> to use 741s in systems, instead of 709s. The 741s were a lot more
> expensive at the time.
>

It's been a bit long ago but I think one reason I liked the 709 better
was because it was not internally compensated so cuold be souped up. Of
course, my class mates only souped up mopeds instead. One of them died
that way :-(

> I wonder what's the oldest IC still in production.
>

Most likely a military chip where we'll never find out the introduction
date unless it's declassified before we all are six feet under.

[John Larkin]

On Thu, 05 Apr 2012 22:58:53 -0400, Spehro Pefhany
<spef...@interlogDOTyou.knowwhat> wrote:

>On Thu, 05 Apr 2012 13:11:04 -0700, the renowned John Larkin
><jla...@highlandtechnology.com> wrote:
>
>>On Thu, 05 Apr 2012 09:32:35 -0700, Fred Abse
>><excret...@invalid.invalid> wrote:
>>
>>>On Wed, 04 Apr 2012 19:59:58 -0700, josephkk wrote:
>>>
>>>> In a way it is really cool, the 723 is older than the 555 and still
>>>> known to be very useful. Kinda like the uA741 and the LM101 as well.
>>>
>>>As I've intimated before, I've had endless fun (not), getting 723s with
>>>added pass transistors, to stop oscillating at HF, in other people's
>>>(commercial) designs.
>>>
>>>The 741 used to latch up.Maybe they've cured that problem in the
>>>intervening years. I stopped using them as soon as I could.
>>
>>741's were OK. It was the 709 that had bad latchup problems, when one
>>of the front-end transistors zenered. I remember, as a kid, deciding
>>to use 741s in systems, instead of 709s. The 741s were a lot more
>>expensive at the time.
>>
>>I wonder what's the oldest IC still in production.
>
>Maybe the SN5400/7400 (ca. 1965)- still shows as "active" on TI's
>website.
>

Sounds like it. The 741 was introduced in 1968, and the 555 in 1971.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

[Jan Panteltje]

On a sunny day (Fri, 06 Apr 2012 19:10:41 -0700) it happened John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote in
<3e8vn713jha1ks6v5...@4ax.com>:

>On Thu, 05 Apr 2012 22:58:53 -0400, Spehro Pefhany
><spef...@interlogDOTyou.knowwhat> wrote:
>
>>On Thu, 05 Apr 2012 13:11:04 -0700, the renowned John Larkin
>><jla...@highlandtechnology.com> wrote:
>>
>>>On Thu, 05 Apr 2012 09:32:35 -0700, Fred Abse
>>><excret...@invalid.invalid> wrote:
>>>
>>>>On Wed, 04 Apr 2012 19:59:58 -0700, josephkk wrote:
>>>>
>>>>> In a way it is really cool, the 723 is older than the 555 and still
>>>>> known to be very useful. Kinda like the uA741 and the LM101 as well.
>>>>
>>>>As I've intimated before, I've had endless fun (not), getting 723s with
>>>>added pass transistors, to stop oscillating at HF, in other people's
>>>>(commercial) designs.
>>>>
>>>>The 741 used to latch up.Maybe they've cured that problem in the
>>>>intervening years. I stopped using them as soon as I could.
>>>
>>>741's were OK. It was the 709 that had bad latchup problems, when one
>>>of the front-end transistors zenered. I remember, as a kid, deciding
>>>to use 741s in systems, instead of 709s. The 741s were a lot more
>>>expensive at the time.
>>>
>>>I wonder what's the oldest IC still in production.
>>
>>Maybe the SN5400/7400 (ca. 1965)- still shows as "active" on TI's
>>website.
>>
>
>
>Sounds like it. The 741 was introduced in 1968, and the 555 in 1971.

I made a nice audio mixer with some 741s, liked it much better than the 709,
no need for that compensation capacitor.
I still have some 741s in the box.

[Jamie]

Putting aside that they need a rather higher bus rail voltage compared
to today's standards, to be usable, I really don't see a reason why a
741 or any of those standards should be put to the grave, just because
they're old?

I still have a lot of them and still use them for generic applications
where precise operation isn't required, which is the case in many
applications these days.

I find that many of today's monolithic op-amps aren't much better or in
some cases worst, than the old 741 and still they get the recognition,
only because they're newer?

It's the same old argument with the 555 timer. Aside from the fact
that they don't operate in the lower voltage world, they have proved to
be something that is hard to kill. There was a 1 Cell 555 timer out
there but for some reason no one is producing them at the moment.

I don't know, that's my take on it.

Jamie

[John Larkin]

741s were notorious for popcorn noise, worse than 709's as I recall.
They were probably OK for line-level mixers, but terrible for
lower-level stuff.

Popcorn is rare these days, but shows up once in a while. We had some
Analog Devices DACs that were terrible... until they discontinued
them.

[k...@att.bizzzzzzzzzzzz]

On Sun, 08 Apr 2012 08:45:30 -0700, Fred Abse <excret...@invalid.invalid>
wrote:

>On Thu, 05 Apr 2012 13:11:04 -0700, John Larkin wrote:
>
>> 741's were OK. It was the 709 that had bad latchup problems, when one of
>> the front-end transistors zenered. I remember, as a kid, deciding to use
>> 741s in systems, instead of 709s. The 741s were a lot more expensive at
>> the time.
>

>I never had any problems with 709s.

I burned many-a-finger breadboarding 709s. The crappy white breadboards ("EL
sockets", IIRC) made crappy contact and when they lost compensation they broke
into smoke. I switched to 741s and got my projects (analog computer circuits)
done. ;-)

[John Larkin]

On Fri, 06 Apr 2012 12:30:19 -0700, Joerg <inv...@invalid.invalid>
wrote:

>John Larkin wrote:
>> On Thu, 05 Apr 2012 09:32:35 -0700, Fred Abse
>> <excret...@invalid.invalid> wrote:
>>
>>> On Wed, 04 Apr 2012 19:59:58 -0700, josephkk wrote:
>>>
>>>> In a way it is really cool, the 723 is older than the 555 and still
>>>> known to be very useful. Kinda like the uA741 and the LM101 as well.
>>> As I've intimated before, I've had endless fun (not), getting 723s with
>>> added pass transistors, to stop oscillating at HF, in other people's
>>> (commercial) designs.
>>>
>>> The 741 used to latch up.Maybe they've cured that problem in the
>>> intervening years. I stopped using them as soon as I could.
>>
>> 741's were OK. It was the 709 that had bad latchup problems, when one
>> of the front-end transistors zenered. I remember, as a kid, deciding
>> to use 741s in systems, instead of 709s. The 741s were a lot more
>> expensive at the time.
>>
>
>It's been a bit long ago but I think one reason I liked the 709 better
>was because it was not internally compensated so cuold be souped up.

An uncompensated 709 made a decent comparator. My first switching
regulator, 24-to-5 volts, was a 709-based hysteretic buck. The 709
drove a 2N2905, then a 2N3055 emitter follower, which didn't saturate
so stayed reasonably fast. I designed it to run around 23 KHz, because
I could still hear 22K in those days.

[John Larkin]

On Sun, 08 Apr 2012 08:45:30 -0700, Fred Abse
<excret...@invalid.invalid> wrote:

>On Thu, 05 Apr 2012 13:11:04 -0700, John Larkin wrote:
>

>> 741's were OK. It was the 709 that had bad latchup problems, when one of
>> the front-end transistors zenered. I remember, as a kid, deciding to use
>> 741s in systems, instead of 709s. The 741s were a lot more expensive at
>> the time.
>

>I never had any problems with 709s.

If the differential input got to be over about 6 volts, one of the
input transistors would zener b-e and the gain could flip sign, sort
of. So a follower could latch up. We added resistors and diodes in
certain circuits to keep them safe. The 741 didn't have that problem.

Still, the 709 was a great gadget, for the time.