Clipper and clamper circuits

Clipper

A clipper (limiter) is a diode circuit that removes (clips) the part of the input signal above or below a chosen level, without distorting the rest of the waveform. It uses a diode, a resistor and sometimes a DC battery to set the clipping level.

• Series clipper: diode in series with the load.
• Shunt (parallel) clipper: diode across the output.
• Types: positive, negative, biased and combination (two-level) clippers.

Example: shunt positive clipper (Si diode, 0.7 V drop)

 vin o--[ R ]--+------o vo
               |
              \ /  D (anode up,
              ---  cathode to ground)
               |
 o-------------+------o

For vin = 10 sin ωt: in the positive half the diode conducts once vin > 0.7 V, so vo is held at 0.7 V; in the negative half the diode is off and vo = vin. Output swings from +0.7 V to −10 V. Adding a battery in series with the diode moves the clipping level (e.g. 3 V battery → clip at 3.7 V).

Uses: wave shaping, protecting circuits from over-voltage, noise limiting.

Clamper

A clamper (DC restorer) shifts the whole waveform up or down by adding a DC level, without changing its shape or peak-to-peak value. It needs a capacitor, a diode and a resistor; the time constant RC must be much larger than the signal period so the capacitor does not discharge noticeably.

Example: positive clamper

 vin o--| C |--+------o vo
               |
              _|_  D (cathode up)
              /_\  anode to ground
               |    R across output
 o-------------+------o

For vin = ±10 V square wave: during the negative half the diode conducts and C charges to 10 V; then vo = vin + 10 V, so the output swings from 0 to +20 V (ideal diode). Peak-to-peak stays 20 V. Reversing the diode gives a negative clamper (0 to −20 V).

Uses: TV receivers (DC restoration), voltage multipliers.