Patent ID: 6031424
Filing Date: 2000-02-29
Classification: H03F

Abstract:
A differential amplifier comprising:a first current source;a first pair of transistors, each transistor in the first pair having a base coupled to an input of the differential amplifier, and an emitter to collector path coupled on a first end to the first current source and on a second end to an output of the differential amplifier;a second pair of transistors, a first transistor in the second pair having an emitter to collector path coupled on a first end to the second end of the emitter to collector path of a first transistor in the first pair and coupled on a second end through a resistive element to ground and having a base connected to a voltage reference, and a second transistor in the second pair having an emitter to collector path coupled on a first end to the second end of the emitter to collector path of a second transistor of in the first pair and coupled on a second end through a resistive element to ground and having a base connected to the voltage reference;a second current source means;a third pair of transistors, each transistor in the third pair having an emitter to collector path coupled on a first end to the second current source means, a first transistor in the third pair having a base coupled to a base of a first transistor in the first pair, and a second transistor in the third pair having a base coupled to a base of a second transistor in the first pair;a first operational amplifier having a first input coupled to the second end of the collector to emitter path of the first transistor of the first pair, a second input, and an output;a first operational amplifier connected transistor having an emitter to collector path coupled on a first end to a second end of the collector to emitter path of the second transistor in the third pair and to the second input of the first operational amplifier, a second end of the collector to emitter path of the first operational amplifier being coupled to the second end of the collector to emitter path of the second transistor in the second pair, and a base of the first operational amplifier connected transistor coupled to an output of the first operational amplifier;a second operational amplifier having a first input coupled to the second end of the collector to emitter path of the second transistor of the first pair, a second input, and an output; anda second operational amplifier connected transistor having an emitter to collector path coupled on a first end to a second end of the collector to emitter path of the first transistor in the third pair and to the second input of the second operational amplifier, a second end of the collector to emitter path of the second operational amplifier being coupled to the second end of the collector to emitter path of the first transistor in the second pair, and a base of the second operational amplifier connected transistor coupled to the output of second operational amplifier.