Accurate peak-to-valley detector circuit

This circuit uses only two operational amplifiers to detect the peak and valley voltages of non-sinusoidal waveforms. During the peak period, D1 is turned on to charge C1 to the peak value. After the peak value, due to the current limiting effect of R1, C1 discharges very little. It will be charged again at the next peak value to maintain the peak voltage output. Valley detection is opposite to the above. During the valley period, C2 is rapidly discharged to the valley voltage through D2, while at other times it is only slightly discharged through D4 and R2, and the valley voltage is always maintained on C2. The 1Ω resistors connected in series on C1 and C2 are used to prevent overshoot.