DEF Amp

The one and only
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I am going to start this thread around the circuit shown at BAF 2016,
seen at the end of the talk on the video, and attached here in simplified
form.

I am calling it DEF, which stands for Depletion / Enhancement Follower.
It is a self-biasing push-pull output stage which has some interesting
characteristics, not the least of which is low temperature drift which allows
stable undegenerated operation.

:wiz:
 

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...I am calling it DEF...

Eh?? :p

Very interesting, though it will be a challenge to find enhancement P-channels whose Vgs matches that of available depletion parts... The IXYS parts all hang around -2V for reasonable bias (<2A), so maybe the 2SJ201 could work. The USCi and Infineon JFETs all require very negative (<-7V) bias, though. Perhaps, once again, the Semisouth part is just special...
 
@ Mr Pass

In follower V2 resitors help selfbiasing for unmatched part's
do they resistors other function in the same time ?
Example schade feedback on enhancement IRFP240 for triode like character ?
 

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@ Mr Pass

In follower V2 resitors help selfbiasing for unmatched part's
do they resistors other function in the same time ?
Example schade feedback on enhancement IRFP240 for triode like character ?

Hello soundhappy. You made an interesting point. A follower using an N device which has a pentode-like characterisic [R085], and P- device which has a triode like characteristic; be it a Schaded FET or a SIT; say 2SJ28. What will the resultant subjective sound be due to mixing a pentode and a triode characteristics?
 
...... It is a self-biasing push-pull output stage which has some interesting
characteristics, not the least of which is low temperature drift which allows
stable undegenerated operation.

The low temperature drift only occurs when the Id-tempco of the PMOS is smaller than that of the NJFET, correct ?

Am I right in saying that it will have more noise than e.g. a Source Follower using a matched pair of NJFETs ?


Patrick
 
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