Diode Application in Clamping: Working & Advantages

Introduction : Clamping circuits utilize diodes to fix the voltage of a waveform to a desired reference level, protecting sensitive components from overvoltage and shaping signals for correct operation. In this application note, we explore how diodes function in clamping circuits, their working principle, and the key advantages they bring in protection, signal conditioning, and preventing harmful voltage excursions.

Diode Clamping Circuit working

Following are the different methods used for clamping.

1. Zener clamp : Back to back zener diodes are used in its implementation.
2. Diode resistor : Series Resistor and shunt diodes are used.
3. TVS clamp : Bi-directional TVS diodes are used.
4. Active clamp : Op-amplifier is controlled.

The figure-1 depicts diode based clamping circuit. It’s main goal is to limit input voltage to safe range and preventing it from exceeding operating limits of components. Let us understand its working.

• Under normal operation, Vin is within safe range (i.e. between 0 to 3.3V) and both diodes are reverse biased. Here these diodes act as open circuits and have no effect on the signal. The voltage passes through series resistor to sensitive input.
• When positive over voltage is there, i.e. when Vin is above Vcc plus forward voltage drop of diode (0.3V - schottky diode, 0.7V - silicon diode). D1 becomes forward biased and voltage at ADC input is limited to Vcc + Vf.
• When negative over voltage is there, i.r. when Vin drops below ground by more than forward voltage drop of the diode, D2 becomes forward biased and ADC input is limited to GND-Vf.

Advantages of clamping diode

Following are key benefits of diode clamping circuit.

1. It protects sensitive components in the circuit by preventing voltage spikes from exceeding safe threshold.
2. It offers fast response time and hence responds nearly instantaneously when forward biased.
3. Basic clamping circuit just requires a diode and a capacitor. Hence it is inexpensive and simple to implement.
4. Clamping circuits preserve or restore baseline or DC offset of a waveform.
5. In many clamper circuits, while DC level is shifted, peak to peak amplitude of waveform is maintained. Hence signal amplitude information is preseved.
6. Clamping is used in many applications which include signal conditioning, voltage regulation, communication systems, ESD protection, waveform shaping etc.

Conclusion: Diode clamping is a straightforward yet powerful technique to protect electronic circuits and maintain signal integrity. With fast response, low component count, and reliability, clamping diodes help avoid damage from surges and transient voltages.