cathode follower DC coupled output
Because the cathode follower B has a DC coupled output.
lineup said:
Because the cathode follower B has a DC coupled output.
Much had been made earlier about each triode seeing the other as
if a constant current source. Yet any reasonable cathode resistor
for bias sake, is not enough to force a triode to a constant current.
Then I seen how some make the dynamic impedance of the upper
triode to increased by adding a choke. And the dynamic impedance
of the lower reduce by adding a bypass cap. Those types of mods
all seem to me leaning away from SRPP, and toward Mu Follower.
Anyway, I had this dumb idea a way back... It may still have some
entertainment value. I have fixed a small error in my prior schematic.
Each triode sees the other as a much higher impedance, and each
operates closer to Mu. The feedback is regenerative (positive) and
only just enough to create a virtual bypass for the lower cathode.
if a constant current source. Yet any reasonable cathode resistor
for bias sake, is not enough to force a triode to a constant current.
Then I seen how some make the dynamic impedance of the upper
triode to increased by adding a choke. And the dynamic impedance
of the lower reduce by adding a bypass cap. Those types of mods
all seem to me leaning away from SRPP, and toward Mu Follower.
Anyway, I had this dumb idea a way back... It may still have some
entertainment value. I have fixed a small error in my prior schematic.
Each triode sees the other as a much higher impedance, and each
operates closer to Mu. The feedback is regenerative (positive) and
only just enough to create a virtual bypass for the lower cathode.
Attachments
KP,
clever circuit - mu follower top end, stock bottom end with fb.
However, is the fb regenerative (positive)? The output phase is opposite to the input and the input triode's cathode; therefore, as input drops neg, cathode drops with it, but output rises pos, and this tries to raise the cathode, reducing bias, and therefore output.
OTOH, the way you dimension it would turn the cathode essentially into a virtual earth, effectively giving it a cap to ground. That would boost gain, and the advantage would be that you could use a 2.2uF fb cap, rather than a 470uF bypass cap. Neat!
I believe it's overall negative feedback, but this is verified of course if the gain is less with the fb than without it.
I'd reckon it would have a gain slightly less than mu, great bandwidth, and very low Zout and distortion.
Hugh
clever circuit - mu follower top end, stock bottom end with fb.
However, is the fb regenerative (positive)? The output phase is opposite to the input and the input triode's cathode; therefore, as input drops neg, cathode drops with it, but output rises pos, and this tries to raise the cathode, reducing bias, and therefore output.
OTOH, the way you dimension it would turn the cathode essentially into a virtual earth, effectively giving it a cap to ground. That would boost gain, and the advantage would be that you could use a 2.2uF fb cap, rather than a 470uF bypass cap. Neat!
I believe it's overall negative feedback, but this is verified of course if the gain is less with the fb than without it.
I'd reckon it would have a gain slightly less than mu, great bandwidth, and very low Zout and distortion.
Hugh
excellent cathode follower idea!
Hello Federico,
you are not joking, it is excellent. 😎
Thanks for sharing this idea. 🙂
Yes, definitely.
Some are annoyed, others don't understand and some play "three monkeys" because of commercial interest.
Your post is three years old ...
Kind regards,
Darius
Hello Federico,
you are not joking, it is excellent. 😎
Thanks for sharing this idea. 🙂
Yes, definitely.
Some are annoyed, others don't understand and some play "three monkeys" because of commercial interest.
Your post is three years old ...
Kind regards,
Darius
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