class C amplifier gain
Kyle Cronan
How can I calculate the gain of a class C amplifier with no bias?
These amplifiers often have little or no emitter degeneration, but I
don't see how to figure the intrinsic emitter resistance when there is
no quiescent current. I understand how r_e is derived from Ebers-
Moll, but this assumes the base voltage is held constant.
I'm guessing it's going to depend on transistor beta given the
operating conditions? Is it not correct to speak of gain in this
situation, because of the nonlinearity? How about output power for a
given drive level?
Thanks for your help,
Kyle
Tim Williams
slightly less than 1, except for that little +/-0.6V offset where nothing
happens. A collector output depends on what's driving the base and how much
collector current that in turn produces.
For small signals, the gain is of course zero, but that's not too useful.
It might be more useful to speak of voltage or power gain at optimal input /
output conditions, in which case you'd probably be reading up on RF amps to
determine that.
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
"Kyle Cronan" <ky...@pbx.org> wrote in message
news:7b27ba6d-e778-4c1a...@s15g2000yqs.googlegroups.com...
Kyle Cronan
> What kind, collector or emitter output? An emitter follower is obviously
> slightly less than 1, except for that little +/-0.6V offset where nothing
> happens. A collector output depends on what's driving the base and how much
> collector current that in turn produces.
>
> For small signals, the gain is of course zero, but that's not too useful.
> It might be more useful to speak of voltage or power gain at optimal input /
> output conditions, in which case you'd probably be reading up on RF amps to
> determine that.
>
> Tim
>
Collector output. I'd like to be able to calculate the gain if I know
the voltage and source impedance at the input. The collector load is
some (possibly complex) impedance up to the positive supply. Emitter
has a small or zero resistance R to ground.
If you can recommend any good books, that would also help. I have the
Art of Electronics and Experimental Methods in RF Design. The problem
is there seems to be a gap between what AoE explains regarding this
sort of thing and what EMRFD assumes from the reader. I also have
Introduction to Radio Frequency Design by Hayward, but it is a pretty
difficult book for me.
Kyle
christofire
"Kyle Cronan" <ky...@pbx.org> wrote in message
news:7b27ba6d-e778-4c1a...@s15g2000yqs.googlegroups.com...
A Class C amplifier certainly has a power gain and an efficiency, but the
active device is usually configured to operate as a switch.
When amplifying RF signals of limited bandwidth, Class C is invariably used
with some kind of filter to reconstruct sine waves from the pulses of
current that flow through the Class-C 'switch' - the simplest form being a
(coupled) parallel tuned circuit. At the very least, ITU regulations limit
the extent to which harmonics of signals can be radiated. The apparent
power gain, and then the efficiency, of a Class-C amplifier is determined by
the loaded Q of the filter amongst a few other factors.
With each input cycle, the active device biased to work in Class C passes
current for a fraction of the cycle, less than 50%. The amount of current
depends on the input drive, the device characteristics, what the device is
connected to (i.e. the filter) and the power supply. The pulses of current
applied to the filter result in a sine-wave component of current that can be
fed to the system output port (plus harmonic components that may need to be
further filtered out). The strength of the resulting fundamental sinusoidal
component can be found from the Fourier component of the current pulses at
the fundamental frequency. Higher Q reduces loss in the system so it
increases the efficiency, and reduces the strength of harmonic components in
the output signal. Push-pull is very common, not least because it cancels
the second harmonic which could otherwise be expensive to clean up
sufficiently to meet the ITU rules. It also allows cheaper devices to be
used.
Chris
Jan Panteltje
<ky...@pbx.org> wrote in
<7b27ba6d-e778-4c1a...@s15g2000yqs.googlegroups.com>:
>Hi,
>
>How can I calculate the gain of a class C amplifier with no bias?
In my view a class C driving a tuned circuit is basically a switch with less then 50% 'on' time.
For switching you will like to drive the transistor (or MOSFET) into saturation.
This will also have to be done fast enough.
So you are faced with beta (current gain) and hole storage time in case of a transistor.
Ccb wil also try to reduce switching time and lower impedance.
You will need to 'overdrive' the thing.
I think 'gain' is not the right word here, just treat it as a switcher.
MOSFET seems attractive as a switch here ?
Vladimir Vassilevsky
I assume this is RF amplifier with the sine wave input, the filter
source and the filter load. First, you should determine the angle of
conduction of the transistor. Then, assuming the collector current is a
piece of the sine wave, apply the Fourier to find the power of the
fundamental component at the output.
The angle of conduction is determined by the input drive amplitude and
the bias. The collector current depends from the input drive level,
supply voltage, source and load impedances and the C-B capacitance;
other parameters are less important.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
MooseFET
How to work it out in a spread sheet:
The gain depends on the input because the stage is very nonlinear.
The transistor (or diode) equation will tell you the current at each
instant in time. You can fill a spread sheet with many points along
the curve to get the current at many times in the cycle. You can then
multiply the current by sin() and cos() functions to get the two parts
of the fundamental and then combine the averages to get the
magnitude.
You can also plug the design into spice and have it do the work.
Vladimir Vassilevsky
MooseFET wrote:
> On Aug 21, 9:39 pm, Kyle Cronan <k...@pbx.org> wrote:
>
>>Hi,
>>
>>How can I calculate the gain of a class C amplifier with no bias?
>
> The gain depends on the input because the stage is very nonlinear.
> The transistor (or diode) equation will tell you the current at each
> instant in time.
The strong feedback through C-B capacitance determines the behavior of
the stage. Since the load of the stage is LC, the collector voltage is
close to the full sine wave. So the inherent nonlinearity of the
transistor is not that important; what matters is the angle of
conduction. You have to solve the equation including the source and the
load impedances, Ccb and Vcc.
You can fill a spread sheet with many points along
> the curve to get the current at many times in the cycle. You can then
> multiply the current by sin() and cos() functions to get the two parts
> of the fundamental and then combine the averages to get the
> magnitude.
>
> You can also plug the design into spice and have it do the work.
Archimedes, Newton and Einstein perfectly dealt without Spice and Matlab :-)
Kyle Cronan
>
> I assume this is RF amplifier with the sine wave input, the filter
> source and the filter load. First, you should determine the angle of
> conduction of the transistor. Then, assuming the collector current is a
> piece of the sine wave, apply the Fourier to find the power of the
> fundamental component at the output.
> The angle of conduction is determined by the input drive amplitude and
> the bias. The collector current depends from the input drive level,
> supply voltage, source and load impedances and the C-B capacitance;
> other parameters are less important.
>
> Vladimir Vassilevsky
> DSP and Mixed Signal Design Consultanthttp://www.abvolt.com
Okay, so it sounds like the analysis is not nearly as simple as for an
amplifier with a voltage divider for base bias! I'm going to try
simulating some circuits or just trying different collector loads
experimentally.
I get that the transistor is basically acting as a switch. I guess I
was trying to figure out how much gain would be possible before
driving it to cutoff, assuming that there would be clipping. But now
I see that you just let an inductive collector load ring up while the
transistor is cut off. Am I describing that right?
There's something I don't understand: EMRFD is always saying that the
collector "likes to see" a load equal to the supply voltage squared
over twice the output power. Certainly, that's the value you get for
an output sine wave with a maximal peak-to-peak amplitude, equal to
Vcc. But in this case, there are two complications: the harmonics
from nonlinear operation of the transistor, and the ringing up of the
inductor past the positive supply voltage. So how can you justify
starting the design process with this equation? Is it that the two
factors complicating things always exactly cancel each other out?
Thanks for the comments from everyone.
-Kyle
Vladimir Vassilevsky
Kyle Cronan wrote:
> On Aug 22, 9:34 am, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
>
>>I assume this is RF amplifier with the sine wave input, the filter
>>source and the filter load. First, you should determine the angle of
>>conduction of the transistor. Then, assuming the collector current is a
>>piece of the sine wave, apply the Fourier to find the power of the
>>fundamental component at the output.
>>The angle of conduction is determined by the input drive amplitude and
>>the bias. The collector current depends from the input drive level,
>>supply voltage, source and load impedances and the C-B capacitance;
>>other parameters are less important.
> Okay, so it sounds like the analysis is not nearly as simple as for an
> amplifier with a voltage divider for base bias! I'm going to try
> simulating some circuits or just trying different collector loads
> experimentally.
>
> I get that the transistor is basically acting as a switch.
If the transistor is switching, this is Class D. In the class C, the
transistor operation is fairly linear within the angle of conduction.
> I guess I
> was trying to figure out how much gain would be possible before
> driving it to cutoff, assuming that there would be clipping. But now
> I see that you just let an inductive collector load ring up while the
> transistor is cut off. Am I describing that right?
The load of the Class C stage is some sort of resonant circuit; hence
the collector voltage is near sinusoidal.
> There's something I don't understand: EMRFD is always saying that the
> collector "likes to see" a load equal to the supply voltage squared
> over twice the output power. Certainly, that's the value you get for
> an output sine wave with a maximal peak-to-peak amplitude, equal to
> Vcc.
This is correct. Actually, a little bit of overdriving so the amplitude
is slightly higher then Vcc corresponds to the max. power efficiency.
> But in this case, there are two complications: the harmonics
> from nonlinear operation of the transistor,
You are interested in the fundamental component of the collector
current, which depends on the angle of conduction.
> and the ringing up of the
> inductor past the positive supply voltage. So how can you justify
> starting the design process with this equation? Is it that the two
> factors complicating things always exactly cancel each other out?
Huh?
> Thanks for the comments from everyone.
Kyle Cronan
> Kyle Cronan wrote:
> > I get that the transistor is basically acting as a switch.
>
> If the transistor is switching, this is Class D. In the class C, the
> transistor operation is fairly linear within the angle of conduction.
>
> > I guess I
> > was trying to figure out how much gain would be possible before
> > driving it to cutoff, assuming that there would be clipping. But now
> > I see that you just let an inductive collector load ring up while the
> > transistor is cut off. Am I describing that right?
>
> The load of the Class C stage is some sort of resonant circuit; hence
> the collector voltage is near sinusoidal.
Oh, okay, I think I was looking at a section of the book that
presented a "stress test" in which the drive level is very high and
the LC network is detuned: you get very high collector voltages over
only a fraction of the cycle (because of charge storage, apparently).
These are BJT amplifiers.
> > There's something I don't understand: EMRFD is always saying that the
> > collector "likes to see" a load equal to the supply voltage squared
> > over twice the output power. Certainly, that's the value you get for
> > an output sine wave with a maximal peak-to-peak amplitude, equal to
> > Vcc.
>
> This is correct. Actually, a little bit of overdriving so the amplitude
> is slightly higher then Vcc corresponds to the max. power efficiency.
Wait, if the collector load is resonant, won't the peak-to-peak
amplitude be twice Vcc?
> > But in this case, there are two complications: the harmonics
> > from nonlinear operation of the transistor,
>
> You are interested in the fundamental component of the collector
> current, which depends on the angle of conduction.
Ok, so the harmonics are negligible in terms of power if the collector
voltage is nearly sinusoidal?
christofire
"Vladimir Vassilevsky" <nos...@nowhere.com> wrote in message
news:sKudncA8998Zog3X...@giganews.com...
>
>
> Kyle Cronan wrote:
>
>> On Aug 22, 9:34 am, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
>>
>>>I assume this is RF amplifier with the sine wave input, the filter
>>>source and the filter load. First, you should determine the angle of
>>>conduction of the transistor. Then, assuming the collector current is a
>>>piece of the sine wave, apply the Fourier to find the power of the
>>>fundamental component at the output.
>>>The angle of conduction is determined by the input drive amplitude and
>>>the bias. The collector current depends from the input drive level,
>>>supply voltage, source and load impedances and the C-B capacitance;
>>>other parameters are less important.
>
>> Okay, so it sounds like the analysis is not nearly as simple as for an
>> amplifier with a voltage divider for base bias! I'm going to try
>> simulating some circuits or just trying different collector loads
>> experimentally.
>>
>> I get that the transistor is basically acting as a switch.
>
> If the transistor is switching, this is Class D. In the class C, the
> transistor operation is fairly linear within the angle of conduction.
Not generally true. It is advantageous for efficiency in a Class-C
amplifier to have the device operating either at saturation or cutoff.
There is no benefit to 'linear operation' when the inherent degree of
distortion is so great that it requires a tuned circuit to reconstruct the
output signal. http://en.wikipedia.org/wiki/Electronic_amplifier#Class_C
has some of the details, and also attempts to illustrate differences between
classes C and D. The latter also involves switching devices but in Class D
the input signal is modulated using PWM (or PRF modulation, or suchlike) and
the output signal is low-pass filtered - effectively to demodulate it.
Class C is often used to amplify an unmodulated signal (e.g. in RF
multiplier and driver stages) and is fine for amplifying constant-envelope
signals such as FM/phase modulated signals. However, amplification of
signals like SSB and AM that require linearity to avoid generation of
in-channel intermodulation products usually demands the quasi-linear
characteristics of Class AB, or Class B in push-pull. Some AM transmitters
use Class-C output stages with high-level modulation: the power supply
voltage to the switching Class-C stage(s) is varied by the modulating
signal.
Chris
Tim Williams
news:DrCdnZ3RcPu8DQ3X...@bt.com...
> Not generally true. It is advantageous for efficiency in a Class-C
> amplifier to have the device operating either at saturation or cutoff.
> There is no benefit to 'linear operation' when the inherent degree of
> distortion is so great that it requires a tuned circuit to reconstruct the
> output signal.
Sure there is. Driving that capacitor when it's not at exactly 0V takes an
awful lot of power. Switching hard into that load burns up your switch.
A simple and easy to construct example is a blocking oscillator (which, in
the tuned case, is basically a self-excited class C oscillator). Set it up
with a resonant load and you'll only get terrible efficiency -- the
transistor burns so damn much power trying to drive that capacitor, and the
capacitor needs to be fairly large to get a moderate Q at the low impedances
involved. However, operate it in blocking mode (no cap, time constant
determined by bias current and inductance) and you can basically run without
a heatsink. Beautiful square waves, high efficiency -- high harmonic
content.
The point of class C is to use a minimally maximum drive: just enough to
saturate *on the peaks*, not so much that you burn all your efficiency on
the flanks of conduction.
MooseFET
> MooseFET wrote:
> > On Aug 21, 9:39 pm, Kyle Cronan <k...@pbx.org> wrote:
>
> >>Hi,
>
> >>How can I calculate the gain of a class C amplifier with no bias?
>
> > The gain depends on the input because the stage is very nonlinear.
> > The transistor (or diode) equation will tell you the current at each
> > instant in time.
>
> The strong feedback through C-B capacitance determines the behavior of
> the stage.
The OP didn't say anything about the frequencies involved. I left out
the C-B capacitance. Now you are leaving out the E-B capacitance and
the fact that both are lossy and the fact that there is inductance in
all three electrodes and the extra phase shift in the collector
current.
>Since the load of the stage is LC, the collector voltage is
> close to the full sine wave. So the inherent nonlinearity of the
> transistor is not that important; what matters is the angle of
> conduction.
The inherent nonlinearity is important. It is what causes there to be
an angle of conduction in the first place. Also the OP was talking of
the zero bias case. In this case the angle of conduction is large
enough that the transistor can't be assumed to be only conducting at
the point of bottoming as is the typical simplification for the class
C case.
>You have to solve the equation including the source and the
> load impedances, Ccb and Vcc.
>
> You can fill a spread sheet with many points along
>
> > the curve to get the current at many times in the cycle. You can then
> > multiply the current by sin() and cos() functions to get the two parts
> > of the fundamental and then combine the averages to get the
> > magnitude.
>
> > You can also plug the design into spice and have it do the work.
>
> Archimedes, Newton and Einstein perfectly dealt without Spice and Matlab :-)
Yes but just imagine what they could do today with it.
Vladimir Vassilevsky
MooseFET wrote:
> On Aug 22, 8:46 am, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
>
>>MooseFET wrote:
>>
> The OP didn't say anything about the frequencies involved. I left out
> the C-B capacitance. Now you are leaving out the E-B capacitance and
> the fact that both are lossy and the fact that there is inductance in
> all three electrodes and the extra phase shift in the collector
> current.
I assummed the textbook case of the RF power amplifier with the tuned
input and output.
> The inherent nonlinearity is important. It is what causes there to be
> an angle of conduction in the first place. Also the OP was talking of
> the zero bias case. In this case the angle of conduction is large
> enough that the transistor can't be assumed to be only conducting at
> the point of bottoming as is the typical simplification for the class
> C case.
You are correct. The "grid-leak" resistance in the bias path is the
essential parameter.
>>Archimedes, Newton and Einstein perfectly dealt without Spice and Matlab :-)
>
> Yes but just imagine what they could do today with it.
Computer is just a tool of trade; it is very addictive. Probably,
Archimedes could build somewhat bigger catapults, Newton would be caught
in the loop of the further optimization of the accuracy of the
navigation measurements, and Einstein would be probing yet another
numeric models of the wave functions.
Kyle Cronan
no idea how to do the design. This is my situation: I have available
about 26 dBm from the previous stage at a low impedance, less than 10
ohms. I would like to take advantage of this and avoid transformer
matching at the input. I need an output power of 4-5 W. I would like
to avoid the need for any high Q inductors that would need to be hand
wound, but I would like reasonably high efficiency. Ability to
operate over a wide frequency range of 3-7 mhz would be a bonus, but a
bandwidth of several hundred kilohertz would be acceptable.
Can you recommend any books that would help me?
Thanks,
Kyle
MooseFET
> MooseFET wrote:
> > On Aug 22, 8:46 am, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
>
> >>MooseFET wrote:
>
> > The OP didn't say anything about the frequencies involved. I left out
> > the C-B capacitance. Now you are leaving out the E-B capacitance and
> > the fact that both are lossy and the fact that there is inductance in
> > all three electrodes and the extra phase shift in the collector
> > current.
>
> I assummed the textbook case of the RF power amplifier with the tuned
> input and output.
There you go assuming. I have fixed a class-C push pull audio power
amplifier. It sounded just good enough that people could understand
what was said but didn't pass current at idle.
>
> > The inherent nonlinearity is important. It is what causes there to be
> > an angle of conduction in the first place. Also the OP was talking of
> > the zero bias case. In this case the angle of conduction is large
> > enough that the transistor can't be assumed to be only conducting at
> > the point of bottoming as is the typical simplification for the class
> > C case.
>
> You are correct. The "grid-leak" resistance in the bias path is the
> essential parameter.
Unless it is the case where the bias path has a low resistance and the
RF drive has a finite impedance and power at the frequency of
interest. Since the stages input impedance decreases with the
amplitude of the input, a class-C stage can effectively be driven by a
constant power.
>
> >>Archimedes, Newton and Einstein perfectly dealt without Spice and Matlab :-)
>
> > Yes but just imagine what they could do today with it.
>
> Computer is just a tool of trade; it is very addictive. Probably,
> Archimedes could build somewhat bigger catapults,
I liked his idea for the hook and winch system to defend against
ships. You hand these things off the wall of the fort. When a ship
get too close, you hook it and start to wind up on the winch. This
lifts one end of the ship. The other end sinks. You then let go and
down it goes.
The early flame thrower was also a clever idea. It scares the heck
out of the enemy and actually burns the ships to the water line too.
Vladimir Vassilevsky
MooseFET wrote:
> On Aug 23, 8:16 am, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
>
>>
>>I assummed the textbook case of the RF power amplifier with the tuned
>>input and output.
>
> There you go assuming. I have fixed a class-C push pull audio power
> amplifier. It sounded just good enough that people could understand
> what was said but didn't pass current at idle.
You could compensate for the distortion of the output stage by
feedforward from the driver stage. There is a brilliant bridge-type
solution for that; IIRC first used in Quad-405 amp.
>>>The inherent nonlinearity is important. It is what causes there to be
>>>an angle of conduction in the first place. Also the OP was talking of
>>>the zero bias case. In this case the angle of conduction is large
>>>enough that the transistor can't be assumed to be only conducting at
>>>the point of bottoming as is the typical simplification for the class
>>>C case.
>>
>>You are correct. The "grid-leak" resistance in the bias path is the
>>essential parameter.
>
>
> Unless it is the case where the bias path has a low resistance and the
> RF drive has a finite impedance and power at the frequency of
> interest. Since the stages input impedance decreases with the
> amplitude of the input, a class-C stage can effectively be driven by a
> constant power.
Long while ago I've burned (literally) with the VHF Class C BJT
amplifier with R = 0 in the bias path. The R creates automatic bias,
which stabilizes the operation wrt the output load. If the output is
overloaded or underloaded, the operating point of the stage is shifted
so to compensate for it. If R = 0, the stage is more sensitive to the
proper impedance matching.
Vladimir Vassilevsky
Kyle Cronan wrote:
This can be built from few discrete components, however the simplest
solution would be using an IC from MiniCircuits. Just follow the
application manual.
Kyle Cronan
>
> This can be built from few discrete components, however the simplest
> solution would be using an IC from MiniCircuits. Just follow the
> application manual.
>
> Vladimir Vassilevsky
> DSP and Mixed Signal Design Consultanthttp://www.abvolt.com
MiniCircuits are not an option due to the expense. Also, I'm trying
to use as few specialized components as possible.
Kyle
MooseFET
> MooseFET wrote:
> > On Aug 23, 8:16 am, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
>
> >>I assummed the textbook case of the RF power amplifier with the tuned
> >>input and output.
>
> > There you go assuming. I have fixed a class-C push pull audio power
> > amplifier. It sounded just good enough that people could understand
> > what was said but didn't pass current at idle.
>
> You could compensate for the distortion of the output stage by
> feedforward from the driver stage. There is a brilliant bridge-type
> solution for that; IIRC first used in Quad-405 amp.
The class-C amplifier in question used 6L6s IIRC. They where driven
by a transformer circuit that I never quite figured out at the time.
The output was a transformer that sent a nominal 100V signal to where
the speakers were. The design seemed to be optimized to use as few
tubes as you can to make as much noise as you can. I doubt that much
time was spent on sound quality.
[....]
> Long while ago I've burned (literally) with the VHF Class C BJT
> amplifier with R = 0 in the bias path. The R creates automatic bias,
> which stabilizes the operation wrt the output load. If the output is
> overloaded or underloaded, the operating point of the stage is shifted
> so to compensate for it. If R = 0, the stage is more sensitive to the
> proper impedance matching.
Yes it is a nice idea.
These days, I have to use MOS parts in the output and the RF power is
not for radiation. The biggest issue I had was making the RF have as
little near carrier noise as I could without making things run too
hot. Class C with a very strong gate drive and a very quiet power
supply turned out to work the best. With bipolars it seemed that a
large value of bias resistance and running the part short of bottoming
worked the best. The noise that matters is from about 0.01Hz to
500KHz offset from the carrier. I can't trust the high Q to clean it
up because I just can't seem to get inductors with a Q over a billion
or two.
JosephKK
Sometimes those mode variations are also called Class S. Usually for
RF amplifiers only.
Moreover this technique (for AM use) has issues with expensive
filtering for the first few harmonics, especially at significant power
(>10 W).
JosephKK
I wasn't aware that mini-circuits had products in that low frequency
and higher power corner of the market.
--
Transmitted with recycled bits.
Damnly my frank, I don't give a dear
----------
George Herold
I use to have two books that were a collection of application notes on
RF amplifiers from Motorla. That was back in the early 90's. I
learned everything I use to know about RF from them. They grew legs
one day and walked away... sigh. I can't remember the names and a
quick search of the web didn't turn up anything that looked familiar.
But perhaps someone here will know and we can both find used copies on
the web.
George H.
Phil Hobbs
The ones with the nice suede-texture covers? The one I have is "Radio,
RF, and Video Applications", DL413/D, 1993.
Cheers,
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
George Herold
>
> - Show quoted text -
Hmm, That name does not ring a bell, but that might be it. The date
is certainly about right. The ones I had were blue colored
paperbacks. (at least that's my memory) There was a second skinnier
volume that might have been a product selection guide. Would you
recommend "Radio, RF, and Video Applications" to someone learning RF
amplifier design? That was my situation at the time and I remember
them fondly....
George H.
Phil Hobbs
Dunno--I'm not a big RF expert, but what I know about it, I mostly
learned from colleagues. It has a lot of designs for PAs based on old
transistors.
Cheers
George Herold
>
> >> - Show quoted text -
>
> > Hmm, That name does not ring a bell, but that might be it. The date
> > is certainly about right. The ones I had were blue colored
> > paperbacks. (at least that's my memory) There was a second skinnier
> > volume that might have been a product selection guide. Would you
> > recommend "Radio, RF, and Video Applications" to someone learning RF
> > amplifier design? That was my situation at the time and I remember
> > them fondly....
>
> > George H.
>
> Dunno--I'm not a big RF expert, but what I know about it, I mostly
> learned from colleagues. It has a lot of designs for PAs based on old
> transistors.
>
> Cheers
>
> Phil Hobbs
>
> --
> Dr Philip C D Hobbs
> Principal
> ElectroOptical Innovations
> 55 Orchard Rd
> Briarcliff Manor NY 10510
> 845-480-2058
> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text -
>
> - Show quoted text -
Maybe not an expert, but you know way more than me... (I've read your
book after all.)
My only colleague at the time was barely more knowledgeable than
myself. (but it's good to have at least one colleague.)
If PA stand for pulse amplifier then it could be the book. I was
building the amp stage for a 17MHz NMR... 1mW in and a few watts
out... but only for a couple of microseconds every second or so.
George H.
Jeroen Belleman
> I use to have two books that were a collection of application notes on
> RF amplifiers from Motorla. That was back in the early 90's. I
> learned everything I use to know about RF from them. They grew legs
> one day and walked away... sigh. I can't remember the names and a
> quick search of the web didn't turn up anything that looked familiar.
> But perhaps someone here will know and we can both find used copies on
> the web.
>
> George H.
Those notes were probably written by Helge Granberg. I haven't checked,
but many of them are likely float around the web by now. I have many of
them in a loose stack at home.
Jeroen Belleman