Rohm Co., Ltd.

Kengo Adachi

Masanori Fujisawa

Sachito Horiuchi

Taichi Hoshino

Hiroaki Ando

Masato Kobayashi

Eitaro Oyama

A semiconductor amplifier circuit comprises a semiconductor substrate of one conductivity type, a well region of the one conductivity type, formed in said semiconductor substrate, a well region defining region of the other conductivity type, including a side wall portion and a bottom portion defining the well region, a first transistor formed in the well region and a second transistor formed on a surface of another portion of the substrate other than a portion on which the well region is formed. When the first and second transistors are in operation, a potential of the substrate is set to a reference potential, a potential of the well region defining region is set equal to the potential of the substrate or set to a value at which a junction between the well region defining region and the substrate is reverse-biased and at least one of the electrodes of the first transistor is set to a potential at which a junction between the well region defining region and the well region is reverse-biased.

Semiconductor amplifier circuit

A DC-DC converter includes an oscillation circuit for oscillating at a predetermined frequency and generating a pulse with a predetermined pulse width, a reference voltage generating circuit for generating a reference voltage, means mounted in the reference voltage generating circuit for slowly rising the reference voltage, a switching circuit for chopping the current inputted from a DC primary electric power source in accordance with the pulse, and feedback control means for stopping/restarting the oscillation of the oscillation circuit on the basis of the voltage that the output of the switching circuit is smoothed and including the reference voltage with a detection voltage upon stopping control, so that the DC-DC converter having a soft starting function is provided with a simple structure and a compact size without utilizing a PWM circuit and a VCO.

DC-DC converter capable of soft starting function by slowly raising reference voltage

A differential amplifier circuit which has a pair of transistors capable of differential operation with a predetermined bias voltage and a predetermined bias current being set for the base is combined with a dummy circuit having a transistor with a substantially equivalent load to one member of said transistor pair and which is biased in an equivalent relationship to said one transistor, a current mirror in which the base of an input transistor is not diode connected but connected to the base of an output transistor and supplied at the collector or emitter with a drive current flowing to the base of said transistor in said dummy circuit and in which said output transistor supplies each of the bases of said pair of transistors with said bias current which is substantially equal to the current flowing to the base of said transistor in said dummy circuit, and a control circuit that is connected to the base of said transistor in said dummy circuit and which receives the base voltage of said transistor in said dummy circuit and said predetermined bias voltage to maintain the base of said transistor in said dummy circuit at said predetermined bias voltage.

Audio signal amplifier circuit and a portable acoustic apparatus using

In a regulated power supply circuit which includes a differential amplifier circuit and a current output circuit which receives the output from the differential amplifier circuit, wherein the current output circuit comprises a drive stage transistor which operates upon receipt of an output from the differential amplifier circuit at an input terminal thereof, a current output stage of a MOSFET which is driven by the drive stage transistor and a load resistor for the drive stage transistor connected to the output side thereof, and the load resistor and the drive stage transistor are provided between a power source line and a ground line and the MOSFET is driven by an output taken out via the load resistor.

Regulated power supply circuit

A DC/DC converter including a MOS transistor which is inserted in parallel with respect to a load and between a power source feeding line connected from a battery to the load and a ground line. the converter also has a first control circuit which generates a power of a boosted voltage via switching of the MOS transistor, receives the power of boosted voltage and controls the boosted voltage so as to be at a predetermined constant value in response to the boosted voltage. A bipolar transistor is inserted in parallel with the MOS transistor. A second control circuit receives power from the battery and causes switching of the bipolar transistor to generate a power of boosted voltage. When the boosted voltage is lower than an operable voltage of the first control circuit, the second control circuit is operated, and when the boosted voltage is equal to or more than the operable voltage, the operation of the second control circuit is stopped.

Growing community of inventors

Kyoto, Japan

Kengo Adachi