S
Simon S Aysdie
- Jan 1, 1970
- 0
POWER gain IS the requirement.
That's what I always thought. One doesn't, per se, care about "gain"
from the negative resistance viewpoint either.
POWER gain IS the requirement.
I don't have access to this paper.
Budak also has some coverage of RC circuits w/ v-gain, IIRC.
Presumably one could cascade such circuits.
That's what I always thought. One doesn't, per se, care about "gain"
from the negative resistance viewpoint either.
One could certainly cascade them (I'm assuming you mean without an
intermediate buffer), but would you expect the cascade to have voltage
gain? Care to guess what the result will be with the network we've been
discussing? I'll run the analysis and report the result.
Certainly the voltage gains would multiply, if the component values
were right. But the impedances would get crazy fast.
When you said "such circuits", I assumed you meant the very circuit we've
been discussing, the one in the oscillator on the referenced web page. I
didn't realize you intended "such circuits" to mean something like "similar
circuits, but with varying impedance levels". With that meaning, I suppose
that cascading might give even more gain. But, Epstein showed in his paper
that the maximum gain that a passive network can have is 2. So, if one
cascaded networks with impedance levels going up by an order of magnitude
or so ad infinitum, one would think that the voltage gain would be
unlimited. What would cause the voltage gain to remain below 2?
The Phantom said:When you said "such circuits", I assumed you meant the very circuit we've
been discussing, the one in the oscillator on the referenced web page. I
didn't realize you intended "such circuits" to mean something like "similar
circuits, but with varying impedance levels". With that meaning, I suppose
that cascading might give even more gain. But, Epstein showed in his paper
that the maximum gain that a passive network can have is 2. So, if one
cascaded networks with impedance levels going up by an order of magnitude
or so ad infinitum, one would think that the voltage gain would be
unlimited. What would cause the voltage gain to remain below 2?
Greater than 2 seems certainly doable. Did Epstein add some of those
weasely "yes but's" or "assuming ... "?.
Can anybody post the paper?
Could have fooled me; the two look exactly like a darlington emitterJohn said:The signal input to the right transistor is not from an emitter follower.
I'm up at 1e11!.John Larkin said:You'd think that if you can get a stage gain of, say, 1.1 with maybe a
100:1 loading ratio, then 10 stages would get you above 2. Spice could
do that, but the real world probably can't.
100^10 is a bunch of ohms.
John
The said:At this site:
http://www.4qdtec.com/singen.html
there is a schematic titled "A Practical Twin-T Oscillator".
In the text under the schematic we find:
"Now hold on a minute: an emitter follower has no voltage gain and surely
you've been taught that an R-C oscillator must have voltage gain? Well this
one works and has no voltage gain (of course it does have current gain)."
The schematic does show two emitter followers closing the loop. One would
think this couldn't work, but the poster says it does.
Is Barkhausen wrong?
At this site:
http://www.4qdtec.com/singen.html
there is a schematic titled "A Practical Twin-T Oscillator".
In the text under the schematic we find:
"Now hold on a minute: an emitter follower has no voltage gain and surely
you've been taught that an R-C oscillator must have voltage gain? Well this
one works and has no voltage gain (of course it does have current gain)."
The schematic does show two emitter followers closing the loop. One would
think this couldn't work, but the poster says it does.
Is Barkhausen wrong?