Hi! I am trying to amplify a 3-3.5V PWM signal to a 5V PWM signal, frequency may range from 500Hz to 5kHz. I created a schematic in simetrix using a non-inverting op-amp(LM139), the figure is shown below. Although I managed to create a PWM signal with 5V amplitude, the frequency somehow became 10kHz (from 1 kHz) and there is a triangular wave form in the Voff part of the PWM. Can you please tell me the problem here, or if there are any other ways to amplify a PWM signal more efficiently? Thanks very much!
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