Re: amplify 40kHz audio signal using TL082: first two stages are fine, but high noise from the third stage

From: Fred Bloggs (nospam_at_nospam.com)
Date: 03/17/05 

Date: Thu, 17 Mar 2005 11:16:03 GMT

Joerg wrote:
> Hello Tim,
>
>> Joerg, you do _everything_ with plain transistors.
>
>
> Not everything, only when it is cheaper. At two cents a pop these things
> are a bargain. But, I did use a 14106 recently. As a current controlled
> oscillator...
>
> Seriously, in this case it just might make sense to do it with
> discretes. When you need lots of gain at frequencies above the audio
> range things get to be expensive with chips.

He can use a dog-simple hex inverter out of that 4000 series you like so
much- simple discrete FET source follower Sallen-Key 40kHz bandpass Q=10
  ac-coupled into input chain and logic compatible square wave burst
output.