Voltage regulator

摘要

A voltage regulator includes a two-stage feedback circuit for driving a controller formed by a transistor 10. The feedback circuit includes an error amplifier 30 and an output amplifier 20, a simple compensating circuit in the form of a resistor RSZ inserted between the inverting input 22 and the non-inverting input 24 of the output amplifier 20 resulting in a high phase reserve of the feedback circuit. The resistor RSZ limits the gain of the error amplifier 30 for small load currents by reducing its effective output impedance. This compensating circuit results in the two-stage feedback circuit being highly stable even when very low load currents are involved. This now makes it possible to achieve a very simple linear voltage regulator architecture totally integrated on a single chip. It is especially in battery-powered handhelds such as e.g. mobile phones or electronic organizers that this is important since these devices are often on standby with a low current consumption and activated for use only occasionally.