Patent ID: 6285256
Filing Date: 2001-09-04
Classification: H03F

Abstract:
A unity-gain amplifier comprising:an input for receiving an input voltage;an output having an output voltage;a first differential amplifier, receiving the input voltage and the output voltage, for generating a first voltage on a first node, the first voltage rising when the input voltage rises above the output voltage;an inverting stage, coupled to the first node, receiving the first voltage, for generating a second voltage on a second node, the second voltage falling when the first voltage rises;a pull-up transistor, having a gate coupled to the second node, for driving a source current to the output, the pull-up transistor driving a larger source current when the second voltage is falling;a second differential amplifier, receiving the input voltage and the output voltage, for generating a third voltage on a third node, the third voltage falling when the input voltage rises above the output voltage;a pull-down transistor, having a gate coupled to the third node, for driving a sink current from the output, the pull-down transistor driving a smaller source current when the second voltage is falling; anda bias-voltage generator, coupled to the first differential amplifier and the second differential amplifier, for generating a bias voltage that is independent of the input voltage and the output voltage, the bias voltage being applied to the first and second differential amplifiers;wherein the pull-up transistor drives a larger current but the pull-down transistor drives a smaller current when the input voltage rises above the output voltage,whereby the unity-gain amplifier is a push-pull differential amplifier.