I have one problem, I am working on ADC signals and the type of square wave generally obtained has rise and fall time of 10ns roughly and stable level time of 80ns, so in total 100ns ON time. The next sample comes after 50ms approx . For computational purpose I have to stretch the pulse. Hence I am using a peak detector circuit with suitable RC network. Currently I am using OPA657N and 1N4148WT diode. The critical part is that the input signal amplitude varies from 100mV to 5 volts . So diode will be a problem in peak detector. It would be helpful if you could suggest me circuit or application specific opamp(part number).