Abstract: An LED drive circuit includes a booster circuit having a first and second capacitors and using a n/m voltage type rectifying switching and a constant current circuit having a MOS transistor as an output transistor. The constant current circuit is connected in series with an LED as a load of the booster circuit to drive the LED with constant current. With this circuit construction, there is substantially no electromagnetic noise generated and it is possible to maintain a terminal voltage of the LED substantially constant according to the diode characteristics of the LED even when voltage ripple appears in an output of the booster circuit due to the n/m voltage boost, by setting the switching frequency at high to absorb the ripple component on the side of the constant current circuit.

Abstract: A voltage drop DC-DC converter includes a switch circuit including a plurality of switches for alternately connecting a first and second capacitors in series and in parallel in response to an output signal of an oscillator circuit oscillating at a constant frequency. An efficient voltage dropping conversion is possible by deriving a voltage divided by the first and second capacitors when the first and second capacitors are connected in series and deriving terminal voltages of the first and second capacitors when the first and second capacitors are connected in parallel. When the derived voltage is increased beyond an aimed reference output voltage, the oscillation of the oscillator circuit is stopped.

Abstract: A voltage drop DC-DC converter includes a switch circuit including a plurality of switches for alternately connecting a first and second capacitors in series and in parallel in response to an output signal of an oscillator circuit oscillating at a constant frequency. An efficient voltage dropping conversion is possible by deriving a voltage divided by the first and second capacitors when the first and second capacitors are connected in series and deriving terminal voltages of the first and second capacitors when the first and second capacitors are connected in parallel. When the derived voltage is increased beyond an aimed reference output voltage, the oscillation of the oscillator circuit is stopped.

Abstract: An LED drive circuit includes a booster circuit having a first and second capacitors and using a n/m voltage type rectifying switching and a constant current circuit having a MOS transistor as an output transistor. The constant current circuit is connected in series with an LED as a load of the booster circuit to drive the LED with constant current. With this circuit construction, there is substantially no electromagnetic noise generated and it is possible to maintain a terminal voltage of the LED substantially constant according to the diode characteristics of the LED even when voltage ripple appears in an output of the booster circuit due to the n/m voltage boost, by setting the switching frequency at high to absorb the ripple component on the side of the constant current circuit.

Abstract: 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.

Abstract: 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.

Abstract: A regulated power source circuit is provided with a current output circuit including a drive stage transistor which operates when receiving at the input side thereof an output signal from one of transistor for differential operation in a differential amplifier circuit, a current output stage transistor which is driven by the drive stage transistor and a detection circuit which detects a drive current value of the drive stage transistor, and further a dummy circuit which causes to output from the other transistor forming a pair with the one transistor in the differential amplifier circuit a current the value of which is substantially equal to that of the current outputted from the one transistor in the differential amplifier circuit to the drive stage transistor when a detection signal from the detection circuit is received.

Abstract: The present invention resides in an audio amplifier circuit which includes an output terminal of an IC connected to a power amplifier circuit, a resistor having one end connected to a negative feedback input of the power amplifier circuit and the other end connected to a certain terminal other than the output terminal of the IC, a first capacitor connected between the output terminal and a loud speaker and a second capacitor connected between a wiring connecting the output terminal to the loud speaker and the certain terminal. A reduction of low frequency gain determined by a time constant of the first capacitor and an impedance of the loud speaker is corrected by an increase of of low frequency amplification gain determined by a time constant of the second capacitor and the resistor.

Abstract: A data conversion circuit has an input terminal for receiving serial data as time-divided multiple signals, a plurality of sample-and-hold circuits each connected to the input terminal, and output terminals each connected to an associated one of these sample-and-hold circuits to output the received signals as parallel data.