This is the circuit diagram of the simplest single chip AM radio. The circuit is designed around the IC ZN414Z which is a ten transistor tuned radio frequency receiver .The IC has only three leads and is available in the TO92 package. All necessary circuits required for an AM receiver (RF amplifier, detector and AGC are incorporated inside the IC).In the circuit given below, capacitor C1 and resistor R1 forms the tank circuit which is essential for tuning. Capacitor C4 decouples DC from the output of the IC and C1 bye-passes the noise. Transistor Q1 and associated components forms a classic driver stage for the headphone. Head phone is connected across the resistor R5 and R4 gives necessary biasing for the transistor Q1.
- Assemble the circuit on a good quality PCB.
- The circuit can be powered from a 1.5V cell.
- Do not give more than 1.8V to the circuit as it will destroy the IC.
- For L1 make 80 turns of 0.3mm enameled copper wire on a 5cm long ferrite rod.
- K1 can be a high impedance crystal earpiece.