How does this buffer work?
@peskywinnets: Do you know about this: http://www.ant-audio.co.uk/Theory/Application_of_Indirect_Negative_Feedback.pdf
@peskywinnets: Do you know about this: http://www.ant-audio.co.uk/Theory/Application_of_Indirect_Negative_Feedback.pdf
In circuit from post #41 Q3 and Q4 form a CCS loaded Source Follower (search Pass Labs section, B1 buffer).
Q1/Q2 form CCS loaded, triode ("Schade") connected common Source gain stage with a gain of 3V/V (set by R6/R7).
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Yes they are - read the second sentence of post #43. It describes the gain stage of both circuits.
I don't understand - in post #43 i wrote that it is a common Source circuit...
Post #40 doesn't mention a buffer. It shows a circuit that is common-source voltage amplifier (Q1) loaded by CCS (Q2) and wrapped in triode/Schade feedback network (R6/R7) that sets the gain at 3V/V.
Post #41 says that, if need arises, buffer can be added to an existing common-source gain stage and the circuit shows how it's done - Q3 and Q4 are introduced.
Now we come to the obvious mistake in the drawing: there is one wire too much on it, the one that connects lower ends of R4 and R9.
Q3 is a source-follower loaded with CCS (Q4) and together they form a buffer stage.
Both stages (Q1/Q2 common-source gain stage and Q3/Q4 buffer stage) are wrapped in R6/R7 feedback network that sets the gain at 3V/V.
Here is a drawing without a superfluous wire:
Post #41 says that, if need arises, buffer can be added to an existing common-source gain stage and the circuit shows how it's done - Q3 and Q4 are introduced.
Now we come to the obvious mistake in the drawing: there is one wire too much on it, the one that connects lower ends of R4 and R9.
Q3 is a source-follower loaded with CCS (Q4) and together they form a buffer stage.
Both stages (Q1/Q2 common-source gain stage and Q3/Q4 buffer stage) are wrapped in R6/R7 feedback network that sets the gain at 3V/V.
Here is a drawing without a superfluous wire:
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