Make a simple AM ​​radio with digital circuit

Make a simple AM ​​radio with digital circuit

Here is a simple radio circuit made of CMOS digital circuit CD4011, which has high radio sensitivity. CD4011 is a digital integrated circuit containing 4 NAND gates.

Principle: Usually, this type of NAND gate circuit is in two switching states, that is, outputting high level and low level. In fact, there is a transition zone in the conversion process between high and low levels, and the middle part of the transition zone is basically in a linear state. Therefore, the feedback circuit can be used to select the appropriate working state so that each NAND gate is in an amplified state.

The following is the electrical schematic diagram of the radio. L1 and C1 are the receiving resonant circuit, R1 is the DC negative feedback resistor, and C2 is the AC bypass. The received signal is amplified by gate A at high frequency, coupled by C3, and sent to the voltage doubler detection circuit composed of D1, D2, R2, and C4 for detection. It is further amplified by gates B, C, and D and sent to the headphone output. C1 in the figure can be selected as a single variable capacitor, and the coil L can be wound with 80-100T on a 50MM magnetic rod. High-impedance headphones should be selected for the headphones. You can also add a first-level integrated audio amplifier circuit such as LM386, or use a transistor for impedance transformation. By increasing and decreasing the number of turns of the coil on the magnetic rod, ensure that the radio is within the appropriate frequency reception range.