Which device has two base leads?

The correct choice is the unijunction transistor, which is designed with two base leads. In a unijunction transistor, one of the key features is the presence of a single junction formed between a p-type material and n-type material, which effectively creates two terminals for base connections. These base leads are crucial for controlling the device’s functionality, allowing it to operate as a switching element or oscillator in various applications.

Unijunction transistors are primarily utilized in applications such as timing circuits, where the ability to trigger at specific voltages is important. The distinctive design with two bases (often referred to as base 1 and base 2) enables varied control over the operation of the device, particularly in generating pulses or signals.

Other devices mentioned in the question do not possess this specific configuration of two base leads. While the PNP transistor does have two base connections, its overall construction and operation differ significantly from that of a unijunction transistor. The same applies to the PN junction diode, which operates based on a different principle and doesn’t feature multiple base leads. The Zener diode is a specific type of diode designed primarily for voltage regulation, and it also lacks the two base lead configuration characteristic of unijunction transistors. Thus, the