I'm trying to built a voltage regulator using LM324 comparator to used later in controlling the H-bridge to get a pure sine wave output, here are the circuit is shown below :
I have an non-stable output when I implement it. I got an oscillating out-put square wave (15KHz Due to the input capacitance of the PMOS).
I tried to convert this comparator to a difference amplifier to reduce the gain my be it will be more stable, put it still gives me the same problem on the simulation only.
Could you please provide me with your suggestions to improve this design to make it more stable with a constant output voltage.
Q3 increases the loop gain. The extra gain and lag from output to input makes the phase margin negative and causes oscillation.A simple approach is to feed back the high frequency signal directly from output to inverting input.I added a resistor and capacitor on the inverting input pin. I did not assign values but a high C/R ratio improves stability and a low C/R ratio improve frequency response of Vout.
Regards,Ronald MichallickLinear Applications
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