A diode clamp limits AC supply voltage or audio signals to a preset value using one or two Zener diodes in parallel with the power or signal. It can control the amplitude of a signal by clipping half or both halves of the waveform. Zener diodes limit the voltage to a predetermined level, and resistors help produce a well-controlled output voltage. Diode clamps are used in electronic and audio applications to produce low working voltages or compress overly powerful audio signals. They are simple, efficient, and occupy minimal physical space.
A diode clamp is an electronic circuit designed to cut or limit an alternating current (AC) supply voltage or audio signal to a preset value. This is typically necessary when the supply voltage is higher than necessary or if powerful audio signals require compression to avoid overloading. Diode limiter circuits accomplish this clipping function by placing one or two Zener diodes in parallel with the power or signal. A single diode will only cut half of the waveform while a pair of diodes will cut both the negative and positive part of the cycle. Accurate limiting is possible due to the known voltage limiting characteristics of the different Zener diodes.
Any AC power or audio signal consists of a sine or sine waveform. A sine wave is a smoothly repeating series of positive and negative peaks with a zero value in the center of the waveform. The height between these peaks and the zero point defines the amplitude or size of the signal or power. A diode limiter can control the amplitude of a signal if it is too large by clipping half the wave or both. Producing precise amplitude reduction with a diode limiter is possible due to the unique and accurate voltage limiting capabilities of Zener diodes.
This accurate cut-off characteristic allows a Zener diode to limit the voltage it crosses to a predetermined level. If a single diode is driven across the power supply or signal output, it will limit half of the waveform to its rated voltage. If a second diode is inserted into the circuit in the opposite direction or bias orientation from the first, then both the negative and positive halves of the waveform will be limited. These diodes are typically accompanied by one or more resistors in the voltage limiting circuit which help produce a well controlled output voltage.
The diode limiter has many uses in both electronic and audio applications where it is used to produce low working voltages from a single higher supply voltage or to compress overly powerful audio signals. Diode clamps are simple, efficient, and accurate voltage regulators that occupy minimal physical space on printed circuit boards. These circuits are also a particularly convenient way to control voltage outputs. There are also a myriad of Zener diode ratings available which give circuit designers flexibility in the exact voltage produced by the clamping diodes used in their circuits.
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