Olin Lathrop said:
> Yes Mike, I understand how common base works.  Actually this circuit has
> about the same response characteristics as common emitter would with the
> emitter tied to ground (assuming a suitable DC bias arrangement).  In
> either case, small AC input signal is presented directly accross the B-E
> junction of the first transistor.  The small voltage signals there cause
> large (but non-linear) changes in collector current, which is where all
> the voltage gain comes from.
>
>> Negative feedback is right before you.
>
> Again, only DC feedback for bias purposes.

Hi Olin,

I agree with Mike here, you need to study the circuit a little more.
Common-base amps are pretty linear. The negative feedback is degenerative,
but it results in low distortion.

Build it if you don't believe me, put a sine wave in and look at the
output, then pick up a good textbook and read. If you have trouble finding
a good textbook, google for "cascode amps", somewhere in there should be a
description somewhere about the distortion characteristics of common-base
amps.

Cheerful regards,

Bob

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