pwm need to increase frequency

Yup, LM324 is a pitifully slow opamp. And on some of them, all sections screw up if one or more of them is driven open-loop, as two of yours are.

John

Thanks John, Ok, so is there a direct replacement IC or do I need to start over. Mike

I believe a TL 074 / TL 084 will drop in and be an OK starting point.

G=B2

I believe a TL 074 / TL 084 will drop in and be an OK starting point.

G²

In comparing the unity-gain bandwidth I see the LM324 is 1 and the TL084 is 3. I'm not sure that's enough, any changes I can make to the circuit to help? I need to order the part:-( Thanks, Mike

The problem is in the output drivers in the LM324; they are very good at being power-stingy, but not suited (due to crossover distortion) for high-audio-frequency operation. The TL084 uses more quiescent current because it has higher output stage bias current, and lower output impedance. You can also add pullup resistors to an LM324, aim for about 1 mA of current and the outputs of the LM324 will stay in the low-output- impedance condition. That 1 mA of added current is triple the LM324's minimum power requirement, of course.