Two-diode rectifier requirement: A single-phase full-wave rectifier that uses only two diodes will not operate unless which component is present?

Introduction / Context:
There are two common single-phase full-wave rectifier topologies: (1) the bridge rectifier (four diodes, no center tap) and (2) the two-diode configuration that requires a center-tapped secondary. Recognizing the required transformer arrangement prevents miswiring and ensures correct rectification.

Given Data / Assumptions:

• Single-phase AC input.
• Full-wave rectification is desired.
• Only two diodes are to be used.

Concept / Approach:
In the two-diode full-wave scheme, each half of the center-tapped secondary alternately supplies the load while the other diode is reverse-biased. The center tap acts as the return reference, providing the necessary polarity change such that both half-cycles produce current in the same direction through the load. Without a center tap, a two-diode arrangement cannot realize full-wave rectification in the standard manner.

Step-by-Step Solution:

Verification / Alternative check:
Compare with a bridge rectifier that uses four diodes and does not need a center tap. Circuit diagrams show the center tap providing a reference midpoint for alternating halves of the waveform.

Why Other Options Are Wrong:

• Voltage regulator IC / capacitance multiplier / common-mode choke: Not required for basic rectification.
• Phase-inverting transformer: Not a standard component; the needed feature is the center tap.

Common Pitfalls:
Confusing the two-diode full-wave with the four-diode bridge; overlooking the transformer requirements that distinguish them.

Final Answer:
center-tapped transformer