High-precision bipolar limiting circuit

High-precision bipolar limiting circuit

Function of the circuit

This is a limiting circuit that accurately limits the maximum oscillation of analog signals by externally set voltage. It can overcome the shortcomings of ordinary diode limiters. The limiting voltage can be from 0V to the voltage range that the OP amplifier can use. The ability to handle voltages below the forward voltage drop of the diode is the specialty of this circuit.

How the Circuit Works

The OP amplifier is a simple buffer. The resistance values ​​of R2, R3, and R5 are 100K. A1 can also be removed. A2 is an ideal diode circuit with positive output. It can input a negative half-cycle signal. The signal is reversely offset by +VO. A2 can work as an insensitive zone circuit. That is, due to the reverse offset potential of +VO, only a negative input signal with an amplitude higher than this potential can turn on D1.

The input signal is input to A4 as is through resistor R10, and is added to the output of D1 in A4. Therefore, for input signals above +VL, the output of A4 remains unchanged and presents a flat waveform (the top of the sine wave is cut off).

A3 works the same way as A2, but is adapted for positive input signals.