An active peak detector combines an Op-Amp, a diode, and a capacitor to accurately capture and hold the highest voltage level of an input signal. By placing the diode within the Op-Amp's feedback loop, the circuit completely eliminates the standard 0.8V real diode voltage drop. As the input signal rises, the Op-Amp drives the diode forward to charge the capacitor to the exact input level. When the signal falls, the diode blocks any reverse current, perfectly isolating the capacitor so it can maintain the recorded peak voltage.
