Rohm Co., Ltd.

Chung Chien San

Kei Nishioka

Masato Kobayashi

Hiroyuki Funahashi

A semiconductor integrated circuit device is provided with, in a land formed on a semiconductor substrate, a plurality of resistor layers constituted by semiconductor layers of a conductive type reverse to that of the land, and two of the plurality of the resistor layers are connected in series between a supply voltage and a reference potential. The land of the reference potential side resistor layer of the resistor layers connected in series is formed separately from the lands of the other resistor layers, and a voltage lower than a voltage applied to the other resistor layers is applied to the reference potential side resistor layer.

Semiconductor integrated circuit device

A recording/reproducing circuit according to the present invention comprises a recording amplifier for outputting a recording signal, a differential amplifier including a pair of transistors, a base of one of the transistors being a (+) side input, a base of the other transistor being a (-) side input, emitters of the transistors being connected commonly to a current source, the (+) side input being supplied with the recording signal, an output signal being fedback to the (-) side input, the output signal being sent to a recording head and means for cutting a current of the current source to thereby stop an outputting of the recording signal from the differential amplifier circuit.

Recording/reproducing circuit and recording/reproducing apparatus having

An audio amplifier circuit according to the present invention features an arrangement of a power line with a smoothing capacitor inserted as a power filter and a power line without such a smoothing capacitor. The audio amplifier circuit in which an input stage amplifier of a main amplifier is supplied with power via the former power line has a muting circuit for rapidly charging a negative feedback capacitor for generating negative feedback voltage to be fed back from the following stage of the main amplifier to the input stage amplifier up to a voltage level at which a pop sound is inhibited when the power is supplied and for rapidly discharging the negative feedback capacitor up to a reference operating voltage level when the voltage of the former power line with the smoothing capacitor exceeds a predetermined level, the voltage of the former power line being monitored after the power is supplied from a power supply. In this way, the negative feedback capacitor connected to the input stage amplifier of the main amplifier is caused to perform a muting operation by rapidly charging the capacitor up to a level higher than a pop sound level. A point of time the muting operation terminates is determined by a point of time the negative feedback capacitor is caused to start to discharge itself by rapidly discharging the charge of the negative feedback capacitor.

Audio amplifier circuit

A isolation amplifier circuit comprises: an operation amplifier provided with a first and second input terminals, an output terminal, and a feedback resistor for connecting the output terminal and second input terminal; a first emitter follower, for inputting a signal, connected to the first input terminal; a second emitter follower connected between the output terminal and the feedback resistor; a third emitter follower connected between the second input terminal and a first ground impedance; and a fourth emitter follower connected between the first input terminal and a second ground impedance. In the isolation circuit, dynamic resistances of the first, second, third, and fourth emitter followers are made identical with one another.

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Kyoto, Japan

Chung Chien San