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Abstract

An amplifier capable of controlling the magnitudes of quiescent and output current, using externally supplied voltages. The amplifier includes: an input circuit converting a voltage difference between input signals into a current; an output circuit outputting an output current to the outside of the (class AB) amplifier (in response to a change in voltages at the first and second output nodes of the input circuit); a first control circuit generating a first bias current (when a first control voltage is applied), and a first control current; and a second control circuit generating a second bias current (whose magnitude is less than that of the first bias current) when a second control voltage is applied, and a second control current. In a first operating mode the first bias current controls the magnitude of quiescent flowing through the output circuit. The first control circuit and the output circuit form a current mirror. In a second operating mode, the first and second control circuits change the magnitudes of the first and second control currents so as to control the magnitude of the output current. The magnitudes of quiescent current and output current can be easily controlled, and the amplifier can operate stably regardless of external manufacturing process change since there are a few circuit parameter variations.

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