DRIVER CIRCUIT POWERED BY TWO POWER SUPPLIES SEQUENTIALLY ACTIVATED

摘要

A driver circuit including front and rear amplifiers each powered by the primary and secondary power supplies, where the latter power supply is generated from the former power supply. The rear amplifier includes a cascade transistor whose base bias is provided from the bias source. The bias source provides the base bias to reduce the base current when the primary power supply is active but the secondary power supply is inactive, and to be equal to the primary power supply when two power supplies become active but the rear amplifier is inactive.

主权项

1. A driver circuit, comprising:
a front amplifier supplied with a primary power supply; a rear amplifier put in a downstream of the front amplifier, the rear amplifier being supplied with a secondary power supply higher than the primary power supply, the rear amplifier including a current source, a switching transistor, a cascade transistor, and a load resistor connected in series in this order between a ground and the secondary power supply, the cascade transistor being based by a bias source; a booster configured to generate the secondary power supply from the primary power supply, wherein the bias source lowers a base bias of the cascade transistor when the primary power supply becomes active but the secondary power supply is left inactive, and raises to a voltage substantially equal to the primary power supply when both of the primary power supply and the secondary power supply become active but the rear amplifier is left inactive.