Looking for audio op-amp that works well with single supply. LM358?
Bob Wilson
NEIL GANDLER (v064...@ubvms.cc.buffalo.edu) wrote:
: I need an op-amp for low frequency audio amplification (20hz-200hz)
: and low pass filtering. I have several 358 dual op-amps I was going to use.
: I would like to avoid adding a negative supply to my circuitry. So I would
: like to find an op-amp that works well with single supplies. Do op-amps need
: to be specially designed for single supply
: operation or can any op-amp work with a single supply voltage?
: I would appreciate any advice.
:
No not really. The LM 324/358 opamps have PNP input transistors that
allow the input common mode range to extend to (and slightly below) the
negative supply voltage. They also are designed to allow the output to
pull down very close to the negative supply voltage. Both these
attributes are rather handy for single supply work, but not absolutely
essential. The input voltage range in particular is useful, eliminates
the hassle of biasing the input signal into a more limited common mode
range that an opamp with NPN input transistors would have.
Be aware that in the case of an active filter, you will need gain at
well beyond the high cutoff limit that the design of the filter would
indicate. Still, I would venture to guess that a 358 would likely work
for you if the overall gain requirements are low. Otherwise, use a non
compensated opamp, and then compensate it for your particular
application.
Bob.
Steve Weiler
NEIL GANDLER wrote:
>
> I need an op-amp for low frequency audio amplification (20hz-200hz)
> and low pass filtering. I have several 358 dual op-amps I was going to use.
> I would like to avoid adding a negative supply to my circuitry. So I would
> like to find an op-amp that works well with single supplies. Do op-amps need
> to be specially designed for single supply
> operation or can any op-amp work with a single supply voltage?
> I would appreciate any advice.
>
There really is not enough information here. What is the output range
of your sugnal? You give the frequency range but how about the amplitude
of the signal (input and output). Also, what kind of load are you driving?
high impedance... low impedance?
So long as your input and output are within the rails of your supply (less some
range defined in the op-amp's data sheet) you should be ok. Also, you probably
don't need to worry about frquency response as you are only going to 200Hz.
Just put a cap across the feedback resistor and tune it for the cutoff freq
that you want.
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NEIL GANDLER
Winfield Hill
Steve Weiler, <ste...@vikingmem.com> said...
>> ...I have several 358 dual op-amps I was going to use.
Check out LTC part LT1013.
--
Winfield Hill hi...@rowland.org
The Rowland Institute for Science
100 Edwin Land Blvd.
Cambridge, MA USA 02142-1297
Earl Kiosterud
In article <31FCF4...@vikingmem.com>,
Steve Weiler <ste...@vikingmem.com> wrote:
>NEIL GANDLER wrote:
>>
>> I need an op-amp for low frequency audio amplification (20hz-200hz)
use.
>> I would like to avoid adding a negative supply to my circuitry. So I would
>> like to find an op-amp that works well with single supplies. Do op-amps
need
>> to be specially designed for single supply
>> operation or can any op-amp work with a single supply voltage?
>> I would appreciate any advice.
>>
Op-amps don't really know they-re operating with a split supply. They just
see the total rail-to-rail voltage across their supply terminals (usually 30
Volts), and usually have the positive input returned, one way or another, to
the center of this supply ("Ground"). This allows easy input reference, and
easy bidirectional load driving. If the two supply voltages are not equal, it
doesn't matter much to the op-amp. The main effect is that clipping occurs on
one side sooner than the other. If your output signal never goes more than 2
volts from ground, and you power the op-amp with +5 and -25 volts, it'll
generally work just fine (as long as the common-mode input swing of the op-amp
allows operating the inputs this close to a rail, and most do.
Some single-supply op-amps have a built-in "bias" point, somewhere in the
middle of the supply rails. The source signal must be capacitively coupled to
this input. The output is invariably somewhere between the rails, and has to
be capacitively coupled to the load.
If you have a clear need to operate from a single supply, do so, but
split-supply operation is really easier in many ways.
Earl K. Virginia Beach, VA ea...@livenet.net
Bill Sloman
In article <4tjk99$8...@PaperBoy.LiveNet.Net>, ea...@livenet.net (Earl Kiosterud) says:
>
>In article <31FCF4...@vikingmem.com>,
> Steve Weiler <ste...@vikingmem.com> wrote:
>>NEIL GANDLER wrote:
>>>
>>> I need an op-amp for low frequency audio amplification (20hz-200hz)
>>> and low pass filtering. I have several 358 dual op-amps I was going to
>use.
>>> I would like to avoid adding a negative supply to my circuitry. So I would
>>> like to find an op-amp that works well with single supplies. Do op-amps
>need
>>> to be specially designed for single supply
>>> operation or can any op-amp work with a single supply voltage?
>>> I would appreciate any advice.
>>>
>
>
>Some single-supply op-amps have a built-in "bias" point, somewhere in the
>If you have a clear need to operate from a single supply, do so, but
>split-supply operation is really easier in many ways.
>
>Earl K. Virginia Beach, VA ea...@livenet.net
The term "single-supply op amp" seems to be applied to a bunch of
integrated circuit amplifiers designed to offer an input common-mode
range including the negative rail - so you can set the non-inverting input
at ground if you want to - and respectable performace figures with a +5V
supply.
The classic example is the LM324 quad, of which the LM358 is the dual
version. They are cheap, and don't offer particularly high performance.
Linear Technology have some higher performance parts - the LT1006 single
amplifier offers input specs which approach the OP-07, through the
broadband noise voltage is a bit worse at 22nV per root Hz compared with
10nV for the OP-07, but it is a low power device. The LT1013 dual and the
LT1014 quad don't offer quite such low off-set voltages, but still qualify
as precision op amp.
There are micropower version of these amplifiers, in the LT1078 dual
and the LT1079 quad, with a quiescent current of 50uA per amplifier, and
the LT1178 and LT1179, with only 17uA per amp. Broadband noise is worse,
and bandwidth limited (unity gain at around 100kHz).
The Texas Instruments TL2201, and TL2202 "Advanced LinCMOS" amplifiers
offer performance comparable with the LT1006/LT1013, but better broad-band
noise (8nV per root Hertz!) and better output voltage swing, if you trust
the Texas Instrument data sheets.
This isn't a comprehesive list - Maxim has products in this catagory too,
but I haven't plowed through their data books recently.
Bill Sloman
John Lundgren
NEIL GANDLER (v064...@ubvms.cc.buffalo.edu) wrote:
: I need an op-amp for low frequency audio amplification (20hz-200hz)
: and low pass filtering. I have several 358 dual op-amps I was going to use.
: I would like to avoid adding a negative supply to my circuitry. So I would
: like to find an op-amp that works well with single supplies. Do op-amps need
: to be specially designed for single supply
: operation or can any op-amp work with a single supply voltage?
: I would appreciate any advice.
:
: Neil Gandler
I ran into that problem last year with the 1458s, which won't work with
the inputs at the negative rail. The 358s, and also 324s have PNP input
transistors and will work okay with the inputs at the negative rail, which
is the ground with a single supply. But many opamps are not very wide
bandwidth or high slew rate and have problems at the higher audio freqs
and with gains of more than ten. THe opamps may only pass low freqs but
they mmay still have to strain to block the high freqs. So it's wise to
use some that are wide bandwidth and/or low noise. The LF353 or TL082 or
whatever are pin compatible and have wider bandwidth.
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Henry Spencer
In article <29JUL199...@ubvms.cc.buffalo.edu> v064...@ubvms.cc.buffalo.edu (NEIL GANDLER) writes:
>I would like to avoid adding a negative supply to my circuitry. So I would
>like to find an op-amp that works well with single supplies. Do op-amps need
>to be specially designed for single supply
>operation or can any op-amp work with a single supply voltage?
Yes and no.
The op-amp does not really care whether its lower supply voltage is
labelled "-V" or "ground". All it sees is the difference between the
upper voltage and the lower voltage. There may be a minimum value of that
difference for satisfactory operation, but that's the only constraint. An
op-amp which is specced for -5/+5 will run just as happily on 0/+10. Do
watch the minimum difference, though -- one significant advantage of using
an op-amp which is meant for single-supply operation is that its specs
will say something about its performance when operating with small
differences, e.g. 5V (for 0/+5 operation).
The problem you do run into when operating a "dual supply" op-amp on one
supply is input and output ranges. Often, an op-amp cannot handle inputs
which go all the way over to one supply voltage or the other, and cannot
swing its output all the way to one or the other either. With two
supplies, the input and output ranges are conveniently more-or- less
centered on ground. With only one, you may have to design your circuit to
keep inputs between (say) 1.5 and 3.5, and to handle an output that swings
between (say) 0.5 and 4.0. This is a pain; for example, to wire up a
classical inverting-amplifier configuration, with dual supplies you
connect the + input to ground, but with a single supply, you need to
connect it to something like 2.5, which you have to obtain somehow. All
this is an issue even with "single supply" op-amps, but they may be more
tolerant -- for example, often they're willing to accept inputs that go
all the way down to 0.
The bottom line is that there's no fundamental problem with running a
dual-supply op-amp on a single supply, but you have to watch the details,
and the op-amps that are meant for single-supply operation often are
more helpful.
--
...the truly fundamental discoveries seldom | Henry Spencer
occur where we have decided to look. --B. Forman | he...@zoo.toronto.edu
James Brooks
NEIL GANDLER wrote:
>
> I need an op-amp for low frequency audio amplification (20hz-200hz)
> and low pass filtering. I have several 358 dual op-amps I was going to use.
> like to find an op-amp that works well with single supplies. Do op-amps need
> to be specially designed for single supply
> operation or can any op-amp work with a single supply voltage?
>
> Neil Gandler
supply. Feed ground to the Vee of the opamp.
You will have to reference the audio signal to a "virtual" ground. ie a
voltage halfway between Ground and your Vcc. I haven't had much luck
with this. How are you powereing the circuit. If you are using a store
bought power supply (line slug or wall wart) they will usually give you
an ac voltage. This is easy to rectify to both positive and negative dc
voltages and will improve your cicuit.
James Brooks
John Lundgren wrote:
>
> NEIL GANDLER (v064...@ubvms.cc.buffalo.edu) wrote:
>
deleted to save time.
> : I need an op-amp for low frequency audio amplification (20hz-200hz)
> : and low pass filtering. I have several 358 dual op-amps I was going > is the ground with a single supply. But many opamps are not very wide
> bandwidth or high slew rate and have problems at the higher audio freqs
> and with gains of more than ten. THe opamps may only pass low freqs but
> they mmay still have to strain to block the high freqs. So it's wise to
> use some that are wide bandwidth and/or low noise. The LF353 or TL082 or
> whatever are pin compatible and have wider bandwidth.
Don't bother with TL082. It was designed for data communications ie
square waves. It doesn't perform very well with audio signals. Use the
TL072. My current project uses a pair of them. Make sure you reference
your audio to middle voltage if you want to run with a single supply. A
simple resistor network works to split the voltage but you should have
some sort of voltage regulation in the circuit.
Patrick Rea
Drastic Technologies
My thoughts are my own, not the big brass upstairs.
WIZKAP
LM358?
Times have changed, and there are lots of likely candidates that are less
power-hungry, have better distortion and noise characteristics, and have
wider common mode input ranges, etc, etc. Look in the newer Maxim,
Lin-Tech, Mot, and National data books. If you had given specifics, maybe
I could recommend.....
Cheers
Enoch Wexler
v064...@ubvms.cc.buffalo.edu (NEIL GANDLER) wrote:
Consider also using a "Norton" opamp such as National classic LM3900.
While they are terrible for DC applications (*) they work well in AC
applications as yours and are easy to bias in single supply. National
application note AN-72 covers the subject nicely.
(*) Inaccurate current differencing inputs.
BTW, are high precision "Norton" opamps available now?
Regards, Enoch Wexler.
> I need an op-amp for low frequency audio amplification (20hz-200hz)
Duane Waller
James Brooks <jbr...@interlog.com> wrote:
From Duane, yes try the LM3900 Its cheap and is used in many audio,
filtering circuits....You may want to check out National's Lm386
audio 500 Mwatt op-amp which is internally biased for audio
applications. Good sparking!
Scott MacKenzie
In article <4v5u8f$5...@thrush.sover.net> d...@sover.net (Duane Waller) writes:
>From: d...@sover.net (Duane Waller)
>Subject: Re: Looking for audio op-amp that works well with single supply. LM358?
>Date: Sun, 18 Aug 1996 04:10:49 GMT
>James Brooks <jbr...@interlog.com> wrote:
>From Duane, yes try the LM3900 Its cheap and is used in many audio,
>filtering circuits....You may want to check out National's Lm386
>audio 500 Mwatt op-amp which is internally biased for audio
>applications. Good sparking!
Also .. check out the Motorola MC34119...
Regards,
Scott MacKenzie