Patent ID: 6236273
Filing Date: 2001-05-22
Classification: H03F

Abstract:
A monolithic integrated circuit amplifier having an input signal and an output signal comprising:a gain stage that has a gain stage output signal and has, as an input, the amplifier input signal;a buffer stage producing an amplifier output signal and having, as its input signal, the gain stage output signal;an output stage, included within the buffer stage and having at least a first power output transistor that has first and second current terminals and a current control terminal;a first and second voltage supply, the second voltage supply having a relatively higher magnitude than the first;a first power control circuit connected to both the first and second voltage supplies, and to the output stage through a regulator bus;the first power control circuit includinga first switching means connected to the first voltage supply; anda second switching means connected to the second voltage supply;outputs of the first and second switching means both being connected to the regulator bus;in which:when an output demand voltage is less than a predetermined switch-over threshold:current to the output stage is provided substantially entirely from the first voltage supply via the first switching means;the first switching means provides, via the regulator bus, a voltage at the second current terminal of the output transistor that is greater than the voltage at the first current terminal of the output transistor by a predetermined, substantially constant amount; andthe voltage on the regulator bus itself blocks current output from the second switching means; andwhen the output demand voltage is greater than the switch-over threshold:current to the output stage is provided substantially entirely from the second voltage supply, via the second switching means; andthe second switching means provides, via the regulator bus, a voltage at the second current terminal of the output transistor that is greater than the voltage at the first current terminal of the output transistor by the predetermined, substantially constant amount; andthe voltage on the regulator bus itself blocks current output from the first switching means.