Betreff: RE: [sdiy] Re: 4049 and 4069

[Czech Martin]

> Are _all_ MOSFETs so bad, noise-wise?

No, the noise corner can be controlled by gate oxide quality and
surface quality within some limits. And of course, the PMOST
often shows better behaviour than the NMOST in the same process.
In terms of excess 1/f noise they are always worse than bipolar.

You often find mixed designs where the bipolar makes the gain,
and the MOST makes the current with low voltage gain.

Generally the gain/noise characteristics are inferior to bipolar,
as long as we talk about audio and moderate source impedance.

I havn't seen a low noise CMOS input op amp yet. 

When you integrate audio circuits into a CMOS process, it is hell.
Large area devices are always needed.

In the more advanced process generations (0.18u and smaller),
even the PMOST is very bad, analog design becomes more and more
difficult.

m.c.