Waveform out of error amplifier in PWM circuit

For PWM design, an error amplifier inputs are connected with Vref and the feedback signal. As Vref is similiar level with Vfeedback. So, the output of the error amplifier will be liked as a square wave (amplifiered to a VCC) or what is it look like?

Can you post the schematic?

In PWM generation, one input to comparator is a Ramp singal while other is the modulating signal. The output duty cycle is the function of this modulating signal. This forms an open loop system. Now, where are you using feedback in your circuit?