Re: Rectifier-LP filter circuit

On Sat, 10 Nov 2007 20:40:29 -0500, the renowned Fred Bloggs
<nospam@xxxxxxxxxx> wrote:



Spehro Pefhany wrote:
Hi, I'm analyzing a circuit (which I didn't design). It's part of a
meter that outputs a DC voltage related to a 1kHz fairly low-level
square-wave signal. Supply is +/-8 regulated. The JFET op-amps can
handle +/-30V differential input voltage (provided the inputs don't
go below the negative rail in particular).

http://server2.hostingplex.com/~zstoretr/meter.gif

This circuit is a little different from what I'm used to using for the
precision rectification/LPF stages. C7 is polarized, minus on top,
BTW.

Can anyone see a good reason for D3? (or R13 for that matter, other
than to increase the noise)?

Thanks!


Best regards,
Spehro Pefhany

It's not a rectifier, it's an inverting positive peak detector with gain
of 12.1.

Looks like that doesn't it? .. but that's not how it behaves (in
simulation anyway), and not how it functionally has to work.

http://server2.hostingplex.com/~zstoretr/output.gif

The waveform at pin 1 is exceedingly ugly. Looks like it's slew rate
limited.

http://server2.hostingplex.com/~zstoretr/outputa.gif



Best regards,
Spehro Pefhany
--
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Relevant Pages

  • Re: Rectifier-LP filter circuit
    ... Spehro Pefhany wrote: ... handle +/-30V differential input voltage (provided the inputs don't ... simulation anyway), and not how it functionally has to work. ...
    (sci.electronics.design)
  • Re: Rectifier-LP filter circuit
    ... meter that outputs a DC voltage related to a 1kHz fairly low-level ... The JFET op-amps can handle +/-30V differential input voltage. ... precision rectification/LPF stages. ...
    (sci.electronics.design)
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