# Op-amp voltage comparator

I am using an op-amp (LF353P) for my voltage comparator circuit. The supply voltage for the op-amp is +12 V and -12 V. The input voltage for the inverting pin (Vref) is 1.1 V. The input voltage for the non-inverting pin (Vin) is a PWM signal from an ESP32 (1 kHz square wave, 10% duty cycle, Vmax = 2.82 V, Vmin = -318 mV).

The output I got from this is a square wave signal with the same duty cycle as a PWM signal from the ESP32 and a maximum voltage of 23 V and a minimum voltage of -1.60 V.

The output I want is a square wave signal with the same duty cycle as the PWM signal from the ESP32 and a maximum voltage of 12 V and a minimum voltage of -12 V.

I changed my 10 kΩ that connects to the 3.3 V to 20 kΩ for 1.1 V (Vref).

If I understand correctly, if Vin > Vref, Vo is equal approximately to +12 V, and if Vin < Vref, Vo is equal to approximately -12 V.

If I misunderstood, could you explain how it works or how I can get the output I want?

This is the waveform that I get from the op-amp:

• Show waveforms. where is ground on your oscilloscope ? Is it DC coupled or AC coupled ? Aug 15, 2022 at 5:10
• What are you using as the reference, or zero potential node, to read those voltages? Does your opamp +/- 12 V power supply share its 0 V node with the GND symbol on your schematic? Aug 15, 2022 at 5:10
• My opamp +/- 12V power supply is IA1212S and I connected its ground to the ground from esp32. I am using the same ground for my oscilloscope. Aug 15, 2022 at 6:08
• > a maximum voltage of 23 volts and a minimum voltage of -1.60 volts.< ... Why 23 Volts? Aug 15, 2022 at 7:53
• I don't know. I thought it should be +/- 12 volt because my supply voltage is +12V and -12V from IA1212S. Aug 15, 2022 at 7:58