This article introduces a simple radio circuit made of CMOS digital circuit CD4011, which has high radio sensitivity. The CD4011 is a digital integrated circuit with four NAND gates.
Principle: Under normal circumstances, such NAND circuits are used in two states of switching, that is, output high level and low level. In fact, during the transition between high and low levels, there is a transition zone in which the middle portion of the transition zone is substantially linear. Therefore, the feedback circuit can be used to select an appropriate operating state so that each NAND gate is in an amplified state.
The following is the electrical schematic diagram of the radio, L1, C1 is the receiving resonant circuit, R1 is the DC negative feedback resistor, C2 is the AC bypass function, the received signal is amplified by the high frequency of the gate A, and then sent to the C3 The double-voltage detection circuit composed of D1, D2, R2, and C4 is detected, and then further amplified by the gates B, C, and D, and sent to the headphone output. The C1 in the figure can be selected as a single variable capacitor, and the coil L can be magnetized at 50 mm. Around 80-100T on the bar, the earphone should be equipped with a high-impedance earphone. It can also add a first-level integrated audio amplifier circuit such as LM386, or use a triode for impedance transformation. By increasing and decreasing the number of turns on the coil, the radio is suitable. The frequency is within the receiving range.
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