On Tue, 28 Mar 2006 08:59:43 GMT, Patrick Turner
wrote:



Arny Krueger wrote:

"Patrick Turner" wrote in message


They are only as linear as a triode with regard to
voltage gain when external loops of NFB have been applied,
as in the case of the emitter follower connection or
having a few BJTs with a loop of NFB around the
lot of them to correct all their mistakes.

BJTs are inherently non linear for voltage gain and MUST
rely on large amounts of externally connected loops of
NFB.

Simply not true. Local feedback works well with BJTs.

Local loops are externally applied loops of NFB.

Bjts are so damned non linear with regard to voltage gain that large amount of
NFB, local or otherwises must be applied
to linearize the outcome, as well as raise input impedance.

Some BJTs are more linear than say a 300B. Why do you keep ignoring
this *fact*. Heresy?

It isn't ludicous to drag people screaming back to the basics.
The basic fact is that bjts WITHOUT ANY NFB, LOCAL OR OTHERWISE applied anywhere
have hopelessly poor
voltage gain linearity.

Utter bunk, check the spec sheet for the 2SA1216. Gain linearity is
flat as a pancake at elevated junction temperatures, as would be
experienced in a Class A amplifier.

Statements have been made on the group that what i am saying is untrue.

That's because it is - see above.

All opamps also must be used with NFB, and they contain many interconnected bjts
like many
discrete component amplifier, so the non linearity of all these adds together
and must be linearized with NFB.
opamps usually have way too much gain without NFB; and usually poor open loop
bandwidth,
something also flattened out by NFB.

Opamps are *designed* to be used with large amounts of NFB, and a
decent audio opamp such as the B-B OPA2604 is much more linear than
any tube (or combination of tubes) at the same stage gain. How you get
to there doesn't matter, it's the 'black box' performance that counts.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

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