Patent ID: 8031888

Claim:
An electronic apparatus having audio output units, comprising: a multiplicity of output amplifier circuits each having a differential amplifier having a first input terminal for receiving an audio input signal, a second input terminal for receiving a reference voltage, and an output terminal for outputting its output signal, and a feedback resistor connected between said first input terminal and said output terminal, said first input terminal capable of receiving a supplied DC current; a common time-constant circuit having a condenser and a charge and discharge circuit connected to said condenser, said time-constant circuit receiving a direction instruction signal instructing charging or discharging of said condenser, and charging said condenser to a first predetermined charging voltage with a predetermined time constant upon receipt of a direction instruction signal instructing charging of said condenser, but discharging said condenser to a second charging voltage with said predetermined time constant upon receipt of a direction instruction signal instructing discharging of said condenser, said time-constant circuit thereby outputting a charging voltage of said condenser; a common current instruction circuit receiving said charging voltage of said condenser, said common current instruction circuit outputting a first direction voltage that increases (decreases) as said charging voltage of said condenser increases (decreases) and a second direction voltage that decreases (increases) as said charging voltage of said condenser increases (decreases); and a multiplicity of current control circuits, each current control circuit connected to a corresponding one of said output amplifier circuits and receiving said first direction voltage, second direction voltage, a first direction current selection signal, and a second direction current selection signal, and selectively outputting, to said corresponding output amplifier circuit, either one of a first direction current in accord with said first direction voltage, a second direction current in accord with said second directional voltage, a sum of said first and second direction currents, or zero current according to the combination of said first and second direction current selection signals.