Hi Bob,

Thanks for the reply. Please see below.

On Jan 7, 2008 12:52 AM, Bob Blick <bbblick@sbcglobal.net> wrote:

> Current amps, like the common-base amp, are the best you are going to be
> able to do unless you use a transformer. And they are not noiseless,
> although they will be quieter than other topologies. They have their
> quirks, since they are, after all, current amps. And since you are way
> down at 50 ohms all the other resistances are so significant it will
> make it difficult to model.
>
> Beautiful transformers are readily available with 5Hz to 20KHz response.
> They just tend to be rather large and expensive. I'm most familiar with
> 600 ohm input impedance for microphone use but I bet 50 ohms is also an
> off-the-shelf impedance.
>

Yes, I'm not going to go to the expense and size expansion which would
be needed for the transformer.

As for the CB amp, maybe I'm doing the noise analysis wrong, but I'm
getting that it really is no better than a CE amp for noise. I am
modeling the voltage noise source as being in series with the base and
the current noise source between the base and emitter. I'm finding
that with both CB and CE, the voltage noise source is effectively in
series with the input signal (obviously so in the CE, and it is also
true with CB because the base terminal is the "reference voltage" for
the input).

Sean
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