What is a Diode Clamping Circuit?

A diode clamping circuit consists of a combination of one or more diodes and series resistors. It restricts, or "clamps" voltage in a sensitive circuit to levels specified by the circuit designer, to prevent damage to the electronics or for precise control of the circuit's behavior.

Clamping diodes help protect electronic components from voltage spikes due to static electricity. They also limit the voltage to a particular input or output range, in order to either guard against accidental destruction or to make it compatible with a circuit with a lower voltage. The addition of a diode clamp helps solve problems such as these where you need to constrain the amount of voltage in a circuit. In particular, digital logic circuits nearly always feature the use of diode clamps to protect their inputs.

Small signal diodes are commonly used in diode clamp construction. This is because they are specifically created for optimal usage at high frequencies and normally have power ratings less than 0.5 W and current ratings in milliamperes. The 1N914 silicon (Si) diode is a common example.

There are many variations of these circuits. The figure above shows a diode clamp circuit that is limited or "clamped" to a voltage V1 set by a power supply.

A diode clamping circuit may be used to limit the output voltage to a particular range. In the diagram, the input signal is not allowed to rise above 0.7 V or to drop below --0.7 V. This circuit is also called a limiter and is typically used to provide protection to a large amplifier such as a high gain op-amp circuit, as shown.

Diodes only operate properly within a certain range of voltages and currents. If you exceed them, the diode will self-destruct. Be sure to check the manufacturer's specifications to learn what these parameters are.