I have an impulse train of amplitude 1V with constant pulse width \$\tau\$ and I would like to build a circuit that takes this signal and converts it to a constant DC voltage of value \$\tau\$. I can only use opamps, comparators, resistors, DC power supply, diodes and capacitors. How can I build such a circuit?
I thought about using an integrator but this will not really give me the area under the pulse but rather an antiderivative of the signal I believe.
EDIT : In response to a comment of @pipe, here's what I can tell more about the circuit :
- The input impulse train can have a pulse width from [~0 to 300us] that is constant.
- Let's say that my expected values for the output voltage is in mV such that 300mV correspond to a pulse width of 300us.
Best Answer
One resistor and one capacitor, forming a low pass filter, removing everything but the DC component. Unity-gain buffers can optionally be added on the input and output, if necessary to isolate the circuit from external loads.
simulate this circuit – Schematic created using CircuitLab
With a pulse frequency of 1 kHz and component values selected to give a relatively low ripple, this is the result from a simulation in LTspice showing the DC output at levels 10 mV, 100 mV and 300 mV respectively from an input pulse width of 10 µs, 100 µs and 300 µs. If you have a different pulse frequency (though you did not mention anything about that in the question), you can scale the output by inserting a resistor across C1 as a voltage divider, or add a gain before R1 using an opamp.