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

From: John Woodgate (jmw_at_jmwa.demon.contraspam.yuk)
Date: 03/17/05 

Date: Thu, 17 Mar 2005 14:08:14 +0000

I read in sci.electronics.design that for_idea <zhiyang@gmail.com> wrote
(in <1111062045.258039.237360@f14g2000cwb.googlegroups.com>) about
'amplify 40kHz audio signal using TL082: first two stages are fine, but
high noise from the third stage', on Thu, 17 Mar 2005:
>Please! These words are not fair to Larry. His advices have help me last
>night.
>
>I still have one thing not clear: why the signal from first two stages
>is so clean, but after the third one, it suddenly becomes so bad. The
>noise is not oscillation, nor interference. The high spikes of the noise
>keep giving false alarms to the detection circuit.

What is the peak-to-peak output voltage of the second stage? Remember,
your third stage is trying to amplify it 20 times. So if it's more than
about 200 mV, your third stage is overloaded, and if it's very much
overloaded it may well produce spikes. 

-- 
Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Relevant Pages

  • Re: amplify 40kHz audio signal using TL082: first two stages are fine, but high noise from the third
    ... I read in sci.electronics.design that Larry Brasfield <donotspam_larry_b ... 'amplify 40kHz audio signal using TL082: first two stages are fine, ... high noise from the third stage', on Fri, 18 Mar 2005: ...
    (sci.electronics.design)
  • Re: area under curve
    ... John D'Errico wrote: ... > in the higher order integration of Simpson's rule. ... tend to amplify any noise in the ... > more tendency to amplify the noise. ...
    (comp.soft-sys.matlab)
  • Re: Positioning of a Masthead amplifier
    ... >> To ensure you dont amplify nose in the cable. ... > As pointed out previously the cable will generate noise, ... > at the bottom end would amplify noise picked up on the feeder, ... > Please replace invalid and invalid with gmx and net to reply. ...
    (uk.tech.digital-tv)
  • Re: Receiver sensitivity and IF bandwidth??
    ... I.F. would have a HUGE effect on the receiver's signal-to-noise ratio, ... and therefore its sensitivity, if we simply narrowed the IF's ... All an amplifier can do is amplify what's at its input. ... signal is in reference to the noise, that ratio will remain at the output, ...
    (sci.electronics.basics)
  • Re: Low noise amplification
    ... carrrier) prior to digitization. ... should we filter then amplify or amplify ... the question boils down to where the most noise is coming ...
    (sci.electronics.design)