AM diode detector

Fig. below shows a simple diode detector employing a diode and a filter circuit. A detector circuit performs the following two functions.

1. It rectifies the modulated wave.

2. It separates the audio signal from the carrier.

• The modulated wave of desired frequency is selected by the parallel tuned circuit L₁C₁ and is applied to the diode. During positive half cycles of the modulated wave the diode conducts, while during negative half cycles it doesnot. The result is the output of diode consists of positive half cycle of modulated wave as shown in figure.

• The rectified output consists of r.f. component and the audio signal which cannot be fed to the speaker for sound reproduction. The r.f. component is filtered  by the capacitor ‘C’ shunted across the speaker. The value of ‘C’ is large enough to present low reactance to the r.f. component . f_c+f_s  Therefore signal is passed to the speaker.