Patent ID: 6906586
Filing Date: 2005-06-14
Classification: H03F

Abstract:
1. A differential amplifier circuit having a positive-phase input terminal, a negative input terminal, and an output terminal, wherein the differential amplifier circuit provides an output voltage at said output terminal in response to a first differential voltage being applied to said input terminals comprising: a first voltage-current conversion circuit, arranged to convert the first differential voltage into a first current using a first resistor, and to output the first current; an impedance conversion circuit having an input coupled to the output of said first voltage-current conversion circuit and having an output; and a second voltage-current conversion circuit, arranged to convert a second differential voltage, between a reference voltage and a voltage at said impedance conversion circuit output, into a second current using a second resistor, wherein output portions of said first and second voltage-current conversion circuits are connected, and said output of said impedance conversion circuit serves as said output terminal of said differential amplifier circuit, and wherein each of said first and second voltage-current conversion circuits comprises first and second operational amplifiers having an output stage formed by a source follower, positive-phase input terminals of said first and second operational amplifiers are respectively positive-phase and negative-phase input terminals of each of said first and second voltage-current conversion circuits, negative-phase input terminals of said first and second operational amplifiers are connected to an output terminal of the source follower of the output stage, and are connected to each other via the first or second resistor, a drain of a MOS transistor which forms the source follower which is the output stage of said first operational amplifier is connected to an input terminal of a current mirror circuit, and an output terminal of the current mirror circuit is connected to a drain of a MOS transistor which forms the source follower as the output stage of the second operational amplifier, and serves as the output terminal of each of said first and second voltage-current conversion circuits.