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Old 1st May 2012, 01:02 PM   #51
juma is offline juma  Germany
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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:
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