Tool/software:
VU Meter
Based on the Audio signal Input the LED Should Glow
Check and advice
Hi Krishnamoorthy,
Thank you for the diode information. I can't actually run a stability analysis with a diode in the path strangely enough. So for now I'm going to ignore it in the simulations for stability. Not ideal but this is to get a general idea.
You will also notice the circuit has the supply voltage split. That's to make convergence easier within the spice simulator. I also ran the sims twice. Once where the feedback resistor was at a maximum of 100kohms and a second time where it's at 0ohms, representing both extremes. Both of them had less than 1 degree of phase margin. We try to get at least 45 degrees so these circuits are very unstable.
The reason I'm suggesting to go to a lower value is that this large capacitor is causing a massive delay in the feedback network of the op amp.
When I remove the capacitor in the circuit the phase margin becomes 87 degrees. So including the capacitor here actually creates instability.
Capacitor used here for the Filter and Stable output,Advice need to go for lower value ?
What exactly is the capacitor suppose to stabilize here?
For filtering, you could put a capacitor in the feedback loop. The downside is when you change the feedback resistor you change the filter frequency.
If you need to have a capacitor, I recommend including an Riso resistor. More information on how to stabilize an unstable op amp circuit can be found here: Op-Amp Stability Video.
Best Regards,
Robert Clifton
