Diode limiter circuit

The circuit that limits the output signal amplitude is called a limiter circuit. When the input signal amplitude changes greatly, in order to limit the signal amplitude within a certain range, the input signal can be connected to the limiter circuit. For example, in the diode limiter circuit shown in the figure below, the input signal is a sinusoidal AC 5V/1kHz, and its amplitude is about 7V; after passing through the bidirectional limiter circuit composed of dual diodes and dual DC power supplies (±3V), the amplitude of the output AC signal is limited to within 3.7V.

The working principle of this circuit is as follows: (1) When the input signal voltage is higher than 3.7V, diode D1 is in the forward conduction state, while diode D2 is in the reverse biased cutoff state, so the output signal (i.e., the voltage across load R1) is equal to the sum of the conduction voltage drop of diode D1 (0.7V) and the DC voltage (+3V) (i.e., 3.7V); (2) When the input signal voltage is lower than -3.7V, diode D2 is in the forward conduction state, while diode D1 is in the reverse biased cutoff state, so the output signal voltage is equal to the sum of the reverse value of the conduction voltage drop of diode D2 (-0.7V) and the DC voltage (-3V) (i.e., -3.7V); (3) When the input signal voltage is between +3.7V and -3.7V, both diodes are cut off, so the output signal voltage is approximately equal to the input signal voltage (because the resistance value of load resistor R1 is much larger than the resistance value of resistor R2). In summary, the output signal voltage amplitude of this circuit will not exceed +3.7V in the positive direction and will not be lower than -3.7V in the negative direction. That is, no matter how high the input signal amplitude is, the output signal voltage must be limited to 3.7V.