English: Simple diode detector used to extract the envelope of an amplitude-modulated signal. The green AM signal uses a 50 kHz 2 Vpp carrier wave multiplied by a 4 Vpp 1 kHz input sine wave with a 3 V DC offset. The red output signal is the voltage across the capacitor, which is alternatively charged (whenever the AM signal's voltage is higher that the capacitor's voltage) and then discharged through the resistor. The resistor and capacitor values are selected to ensure their RC time constant is low enough so that the capacitor can discharge fast enough to trace the signal as it is falling, but large enough to ensure its cutoff frequency is above the input signal's maximum frequency, to prevent attenuation. This circuit specifically used a 1 nF capacitor and 100 kΩ resistor with a silicon diode.