Precision active peak detector 04 PUBLIC

A precision inverting active peak detector with an output that generates a positive going pulse during the time that the peak holding capacitor is charged.

A precision active peak detector with an output that generates a positive going pulse during the time that the peak holding capacitor is charged.

-1x gain with anti-saturation diode, D1, to stop the opamp o/p hitting -ve rail. This helps the peak detector operate at higher frequencies. The peak detector diode is replaced by an NPN emitter follower, Q1. The collector of Q1 is pulled up to +15V through a resistor and Q2 is connected so that the collector current of Q1 turns it on during the interval that C1 is charged. This generates a positve going pulse during the C1 charging period. pulls up to just below the voltage on the virtgnd net during the whole of the input signal period except when C1 is being charged.

Note that the voltage difference, V(out)-V(prediode) must not be allowed to exceed the base emitter reverse breakdown voltage of Q1.

Note that for unity gain R1 can be removed but R2 must be > 0 otherwise peak detection is defeated! The sweep shows the effect of having D2 or not by setting the value of Rdummy1 to 0 or 1G