Hello everyone am trying to design a pulse width modulation circuit . To generate the PWM pulses i'll feed the triangular wave at one input and a control voltage at the other input of an comparator to get the pulses at the required duty cycle. I need to have a triangular wave which varies from 0 to 5Volt (not a 5volt peak to peak)at a frequency of about 20 Khz. i searched in the internet and found many of the circuits consists of a comparator and integrator to generate the triangular wave which varies peak to peak and those circuits uses a negative voltage supply. My guess is i don't need a negative supply for my kind of circuit design.
I found the formula used to design the integrator which is based on the negative and positive saturation voltages of the op amps.
Am really confused to design this circuit and also for choosing the right op amp with the enough slew rate for a proper triangular wave at the output.
Am just a beginner with the electronics please correct me if i am wrong.
You can use a rail-rail type op amp for the integrator but you will need to add an offset voltage to the (+) input to keep the output within the supply voltage range, since an op amp integrator is an inverter.
Below is a circuit that may meet your needs. You can use other comparators or op amps if they operate from a single-supply and meet your frequency requirements.
You can use a rail-rail type op amp for the integrator but you will need to add an offset voltage to the (+) input to keep the output within the supply voltage range, since an op amp integrator is an inverter.
Below is a circuit that may meet your needs. You can use other comparators or op amps if they operate from a single-supply and meet your frequency requirements.
A lousy old LM358 dual opamp has trouble above only 2kHz.
I would use a OPA034 single opamp (it is low noise and works well at 250kHz). An OPA2134 is a dual opamp. An OPA4134 is a quad.
thanks crutschow can you tell me what would be a better opamp than the LM339 and also what are the features it should have than the LM339 i have choosen.