Question 3-22C5

A three-terminal voltage regulator, such as the common 78xx or 79xx series, is designed to provide a stable, constant DC output voltage despite variations in input voltage or load current. Option **C** accurately describes its internal architecture. It contains: * A **voltage reference** (e.g., a Zener diode or bandgap reference) to provide a stable comparison voltage. * An **error amplifier** that compares a sample of the output voltage to this stable reference. * **Sensing resistors and transistors** to feed the output sample back to the error amplifier and drive the pass element. * A **pass element** (typically a power transistor) controlled by the error amplifier to adjust the output voltage by dropping excess input voltage. Options **A** and **B** are incorrect because a standard three-terminal regulator provides a *single* regulated output voltage, not three. While the current it supplies varies with the load (up to its maximum rating), its primary function is voltage regulation, not supplying current at a constant rate. Option **D** is incorrect; a typical single-output three-terminal voltage regulator employs *one* error amplifier to maintain its regulated output.