LM386 makes an AM radio

The AM radio assembled with two audio integrated blocks LM386N has a larger volume output.

The attached figure is the circuit diagram of the radio. L1 and C1 form a resonant circuit. The received tiny voltage is sent to IC1 for amplification. D1, R3 and C6 are connected to the output end of IC1. It is used to demodulate the high-frequency AM signal. The high-frequency component is bypassed by C6. There is no need to use a low-voltage drop detector diode (such as a germanium tube). The signal amplified by LM386 is enough to overcome the 0.7V voltage drop of an ordinary silicon diode. The final stage uses LM386 to achieve audio amplification, outputting enough power to drive a small speaker, and potentiometer P1 controls the volume.

To increase the stability of the two integrated blocks, the output terminals are connected to RC networks (R1 and C3, R4 and C9), and 47μF capacitors (C2 and C8) are connected to the bypass terminals of each integrated block to suppress the odd harmonics of the power supply voltage. When the battery capacity decreases and the internal resistance increases, it can maintain normal operation.

L1 in the tuning circuit can be wound 100 turns of Φ0.3mm enameled wire on a ferrite rod with a diameter of 10mm and a length of 37mm, and its inductance is 390μH; or 80 turns of Φ0.4mm enameled wire can be wound on a ferrite rod with a diameter of 12mm and a length of 190mm, and its inductance is 550μH.

Note that the first stage is a high-frequency circuit. IC1 and surrounding components should be as close as possible, and even metal shielding should be used to isolate the high-frequency and low-frequency areas.

If you don't add an antenna and don't ground it, the radio effect won't be that good. A few meters of copper wire hanging from the ceiling can be used as an antenna, and connecting it to a water pipe is a good grounding method. For safety reasons, the ground wire in the AC power socket must not be used. The battery voltage is 9v~12v, and the current consumption is 10mA when using a 9V battery.