The gain is set at -10. The prior stage has gain, and off-hand I don't recall how large the signal is, I'll check.
GBW for the part is 8MHz, I run it at 5kHz*10= 50 kHz GBW - plenty of headroom there. SR definition is SR = 2 * pi * f * Vpk So I need SR > 6.28 * 5000 cycles/sec * 15 Volts, or 471,000 Volts/Second. If my math is right, that works out to 0.471 V/uS. Lots of margin there too, the part can do 20. I agree about the linear/saturation description, but couldn't find any hard literature on the subject. I removed all external capacitance, so all that remains is stray - hopefully small. > You say that "The gain is sufficiently large that the opamp is driven > into saturation by the sine wave" but by how much is it driven into > saturation? > > Just near the peaks and troughs or very close to the zero crossings? > great point. Maybe I should increase the gain to force the saturation earlier into the cycle. I was trying just the opposite. Ozzy Lash wrote: > 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 Yeah, I now think this is the case. > As has been alluded to already, the slew rate of the opamp is usually > specified for the device operating in the linear region. If it is > being driven hard into saturation then there will be some recovery > time before the output can drag itself. out of saturation as the > signal changes direction. Yeah, I thought the same thing. Wouldn't that just add delay, but not change the slew rate once it comes out of saturation? > _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user