Re: gEDA-user: opamp slew rate limiting

[Ozzy Lash <ozzy.lash@xxxxxxxxx>]

   On Mon, Nov 9, 2009 at 7:58 PM, <[1]carzrgr8@xxxxxxxxxxxxx> wrote:

     I have a problem with an opamp at work and was hoping someone may
     have some insight.
     This particular opamp is opa2132 from TI, and has slew rate of
     about 20 V/us.  It's driven by a sine wave at 5 kHz.  The gain is
     sufficiently large that the opamp is driven into saturation by the
     sine wave and the slew rate limited edges are very obvious.  The
     rails are +/- 7.5V and it is able to drive to about +/- 6V.  It is
     connected to an old CD40106 schmitt trigger inverter.
     Here's the rub.  The opa2132 doesn't run anywhere near the
     advertised 20V/uS spec.  I see, at best, around 15V / 12 uS, or
     about 1 or 2 V/ uS.

   Are you sure your not just tracking the slow edge of the sine wave?
   Your 12 microseconds is about 20 degrees for your 5 kHz sinusoid.  If
   you increase the frequency does the edge steepen?  Does the slew rate
   go up and down as you increase and decrease the amplitude of the
   sinusoid?  If so, I think that is your problem
   Bill

References

   1. mailto:carzrgr8@xxxxxxxxxxxxx


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