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US 2003/0223601 A1Published application
Electronic apparatus having audio output units
AssigneeRohm Co., Ltd.
InventorsTakenori Kato, Akio Ogura
Life of this patent
Estimating the term…
Abstract
Two control voltages are generated, one increasing and another decreasing, in response to the rise of the voltage of a condenser of a common time-constant circuit. Based on the two control voltages, a first and a second currents are formed, from which four different combinations of currents are established. By feeding one of four combinations to each of multiple differential output amplifier circuits each having a feedback resistor, the multiple output amplifier circuits can be individually started up or shut down without generating popcorn noise, using only one single time constant circuit.
Claims10
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 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 the charging voltage of said condenser;
- a common current instruction circuit receiving said charging voltage, said common current instruction circuit outputting a first direction voltage that increases (decreases) as said charging voltage increases (decreases) and a second direction voltage that decreases (increases) as said charging voltage 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.
6 more elements
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 the output signal of said amplifier circuit, 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 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 the charging voltage of said condenser;
- a common current instruction circuit receiving said charging voltage, said common current instruction circuit outputting a first direction voltage that increases (decreases) as said charging voltage increases (decreases) and a second direction voltage that decreases (increases) as said charging voltage increases (decreases);
- and
- a multiplicity of current control circuits, each current control circuit connected to a corresponding one of said output amplifier circuits and each
- 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 current, or zero current according to the combination of said first direction current selection signal and second direction current selection signal, wherein
- when any one of said multiplicity of output amplifier circuits in operation is shut down, the charging voltage of said time-constant circuit is reversed and the DC current supplied from the corresponding current control circuit is increased;
- when any one of said multiplicity of output amplifier circuits not in operation is started up, the charging voltage of said time-constant circuit is reversed and the DC current supplied from the corresponding current control circuit is decreased;
- and
- when the state(s) of only one or some of said multiplicity of output amplifier circuits are to be changed individually from non-operating state to operating state or vise versa, DC currents supplied from those current control circuits associated with the remaining output amplifier circuits to said remaining output amplifier circuits are controlled not to change through said change of states, irrespective of any change in the charging voltage of said condenser of said time-constant circuit.
10 more elements
Dependencies are inferred from the claim text.