Amplifier White Noise

[Cal Grant]

> Scott Gravenhorst wrote:
> > 
> > I just put together a 2 transistor preamp and I noticed
> > that there is some white noise, even with a shorted input...


<DELURK MODE>

Like the other advisers, I suggest developing most of your needed gain in
the first stage, due to the Friez equation regarding equivalent input
noise.  I would suggest N-channel type FET 2N4341, a very low noise unit.
Set up a moderately high gain common-source amplifier, as the other poster
described.

I would personally go with a extra low noise opamp, such as the LT1128 or
LT1028, or cheaper, the OP27. The LT1124 is also a good choice. There's
always the  5534, which is cheaper. All these units can be run on single
supply if carefully biased, respecting traditional low noise electronic
design rules.

Whatever, keep input sources resistance low and any feedback resistors as
low as possible as well.

cj

<LURK MODE>