Question

Back to back connected Zener diodes are used across the output terminals of a circuit to ________.

• A. prevent unwanted oscillations
• B. provide a constant negative feedback
• C. limit the output positive and negative excursions
• D. avoid back EMF into the original circuit

Hint:

Back-to-back Zener diodes are ideal for waveform clipping and surge suppression. Remember: One diode handles the positive, the other the negative excursion!

Answer 1

The Correct Option is C

Back-to-back Zener diodes are a configuration in which two Zener diodes are connected in opposite directions across a signal line.
Function of Zener diodes in this configuration:
When the voltage across the terminals remains within the Zener breakdown voltage, the diodes do not conduct.
When the signal voltage exceeds the Zener voltage in either polarity, one of the diodes goes into breakdown and conducts.
This effectively clamps the output voltage to a maximum (positive or negative) defined by the Zener breakdown voltage.
Hence, this configuration limits both positive and negative excursions of the voltage signal, thereby protecting subsequent stages from voltage spikes or ensuring signal conditioning.