Question

hey every one there is a circuit given ,,,it is an AM transmitter ,,,,i m confused about how it does work and if any of u have concepts of AM modulation etc plz see it and describe step wise how it is working ??/

Answer 1

http://www.circuitstoday.com/wp-content/uploads/2008/04/am-transmitter1.JPG

Answer 2

Q1, R1-R4,& C5 make up an amplifier circuit (common emitter). Q2, R6, R7, C3, C4, and L1 form an oscillator circuit (Colpitts Oscillator). The condenser (microphone) inputs into the amp which outputs into the oscillator circuit. The input is modulated onto the carrier signal (which vibrates at resonant frequency) of the oscillator. R5 controls the gain that's coupled from the amplifier circuit to the oscillator. For a more rigorous analysis, you should look up "Colpitts Oscillator" and "Common emitter amplifier" in a electrical engineering "Circuits" textbook. Honestly, I don't know that this circuit will perform well. Colpitts oscillators don't drive loads very well.