Final answer:
A transformer center-tap full-wave rectifier circuit requires 2 diodes, where each diode is connected to one end of the secondary winding and allows current flow during alternate half-cycles of the AC input.
Step-by-step explanation:
To form a transformer center-tap full-wave rectifier circuit, you would require 2 diodes. This configuration utilizes a transformer with a center tap on the secondary winding. Each diode is connected to one end of the secondary winding, with their other ends connected together to form the positive output. The center tap acts as the negative output. This setup allows the current to flow through each diode during alternate half-cycles of the AC input, which means one diode conducts during the positive half-cycle and the other during the negative half-cycle. Hence, only 2 diodes are needed to construct a center-tap full-wave rectifier.