Circuit diagram of practical diode detector:
Explanation- The circuit operates in the following manner- The diode has been reversed so that now the negative envelope is demodulated. Due to this negative AGC voltage will be developed.R1 and R2 ensures that there is a series DC path to ground for diode. R1 and C1 is the low pass used to remove RF ripple that is present in the detector o/p. C2 is coupling capacitor that prevents the diode DC o/p from reaching the volume control R4. Hence across R4 demodulated output is with zero dc shift which is applied to the AF amplifier. R3 and C3 is a low pass filter which removes AF components and helps to produce AGC voltage. The DC AGC voltage is proportional to the amplitude of AM signal.