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Eeyore Eeyore is offline
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Default MOSFET output stage



Phil Allison wrote:

"Trevor Wilson"
"RichD"

Who do MOSFET sound better than bipolar, as an audio amp output
driver?


**Non-sequitur. If you're saying that MOSFET outputs sound better, they
don't.

As a device,


** Same old red-herring ******** from know nothing Wilson.

It is totally irrelevant how DEVICES behave on their own.

Only when they are properly configured and suitably biased in a
complimentary output stage can performances be compared.

operating at typical bias currents (say) 10-50mA, MOSFETs
exhibit VASTLY more THD than BJTs.


** UTTER ******** !!!

When configured in typical amplifier topologies, THD is vanishingly small at
all power levels and with minimal bias current.

This is true for LATERAL mosfets as made by Hitachi and Semelab ( ie 2SK176,
BUZ905 etc ).

Switching mosfets ( ie IRFPxxx etc) are not the same.


Yes.

Just for fun once I configured a lateral mosfet output stage with zero feedback.
Its THD at almost all power levels was ~ 1%. From that you can get a good idea
of the negative feedback required to obtain any THD you like.

Lateral mosfets, correctly biased also exhibit virtually NO crossover
distortion. This is all but impossible with bipolars due to their inherent
transfer characteristics unless operated in pure Class A.

Graham