Abstract: A power-factor improved AC-DC converter has a rectifier circuit, a booster converter circuit and a DC-DC converter circuit. A winding on a converter transformer of the DC-DC converter circuit supplies power to both a DC-DC converter control circuit and a booster converter control circuit. In starting up the AC-DC converter, the DC-DC converter circuit is started first, followed by start of operation of the booster converter circuit. With this arrangement, power-factor improved AC-DC converter can be realized with minimum increase in the size and production cost, and the start-up characteristic is improved to avoid failure of start up of the AC-DC converter.

Abstract: A constant-current circuit is disclosed which is arranged such that the magnitude and temperature characteristic of a current flowing through a load can be set independently. Output side of a temperature characteristic setting circuit (15A) connected to a band-gap reference circuit (14), and output side of voltage-follower circuit (16) are connected to a control resistor (R12). The temperature characteristic of the current I0 flowing through the load (13) is set by the band-gap reference circuit (14) and temperature characteristic setting circuit (15A), and the magnitude of the current I0 is set by the control resistor (R12). The arrangement is made such that the magnitude and temperature characteristic of the current I0 can be set independently; thus, the circuit design can be simplified and the the magnitude and temperature characteristic of the current can be set with a high accuracy.

Abstract: The present invention provides an AC-DC converter in which an application range of an AC input voltage can be extended, keeping a voltage in a circuit from rising at a light load. In an AC-DC converter having a rectifier 3, a boost chopper 4 and a DC-DC converter 5, a PWM circuit 6, an one-shot multivibrator 7, a pulse synthesizer 8 and a comparator 9 are further arranged. The pulse synthesizer 8 generates a second pulse signal having a pulse width being narrower by a pulse width of the delay pulse V.sub.pD than that of the first pulse signal V.sub.pa by means of the first pulse signal V.sub.pa which the PWM circuit 6 output s and a delay pulse V.sub.pD generating in said one-shot multivibrator 7. The comparator 9 compares a voltage V.sub.C boosted up by the boost chopper 4 with a reference voltage V.sub.REF to stop generating the delay pulse when voltage V.sub.C drops below the reference voltage V.sub.REF .

Abstract: The present invention relates to a comparator circuit which is arranged such that detected data signal is waveform-shaped without producing any bit error, so that the data signal as transmitted can be accurately demodulated. Reference voltage V.sub.RE of the comparator which is compared with the data signal V.sub.IN is provided by adding output resulting from integration of the data signal V.sub.IN and integrated output of an inverter 2 which inverts output of the comparator 1. The reference voltage V.sub.RE of the comparator 1 can always be located at the center between the high level and the low level of the data signal V.sub.IN despite variations in DC voltage level of the data signal V.sub.IN.

Abstract: In a non-insulated, self-oscillation type DC-DC converter, a first PNP switching transistor (Q1) has the emitter thereof connected to the emitter of a second switching transistor (Q2) of the same conductivity type as the first switching transistor. The base of the first switching transistor (Q1) is connected to the collector of the second switching transistor (Q2). The base of the first switching transistor (Q1) is connected to the base of the second switching transistor (Q2) through a resistor R2. A feedback circuit (4) is connected between the collector of the first switching transistor (Q1) and the base of the second switching transistor (Q2).

Abstract: A small and thin step-up transformer suitable for use in an inverter or the like includes: a bobbin formed of an insulating material having a cylindrical winding shaft; a primary winding wound on said winding shaft; and a secondary winding wound in alignment in multi-layers from the inner side to the outer side thereof; and wherein the primary winding and the secondary winding are separated from each other at a portion of the bobbin to be arranged side by side in the central axial direction of the winding shaft and are electromagnetically coupled to each other.

Abstract: In an FM detector circuit, a phase-shifting circuit is constituted by integrating circuits each consisting of a transconductance amplifier and capacitor. The phase-shifting circuit being arranged to cause limiter signal to be phase-shifted by 90 degrees at center frequency. A multiplying circuit is provided which is arranged to be provided with said limiter signal and output of said phase-shifting circuit, thereby effecting phase-detection of said limiter signal. Further, an error amplifier is provided which is supplied with a smoothed version of detection output derived from said multiplying circuit. The arrangement is made such that output of the error amplifier is applied to the transconductance amplifiers constituting said phase-shifting circuit.

Abstract: A polar leapfrog filter includes at least one polar network. The polar network comprises a differentiator constituted by an operational amplifier having input and output terminals, and a first integrator formed by a first capacitor for providing negative feedback to the operational amplifier and a first variable transconductance amplifier; and a second integrator formed by a second capacitor for providing negative feedback to the first integrator, and a second variable transconductance amplifier. A differentiator is provided at each of the input and output portions of the filter, and a third differentiator is provided immediately preceding the output side differentiator. In the case where two or more said polar networks are incorporated, an additional differentiator is provided between the polar networks. The sum of the number of the circuits constituting the differentiators and the number of the polar networks is selected to be even and equal to the order of the filter.

Abstract: A polar leapfrog filter includes at least one polar network. The polar network comprises a differentiator constituted by an operational amplifier having input and output terminals, and a first integrator formed by a first capacitor for providing negative feedback to the operational amplifier and a first variable transconductance amplifier; and a second integrator formed by a second capacitor for providing negative feedback to the first integrator, and a second variable transconductance amplifier. In the case where two or more said polar networks are incorporated, an integrator is provided between adjacent ones of the polar networks. The total number of all the circuits is selected to be odd and equal to the order of the filter. The adjacent ones of the circuits are connected in such a manner that leapfrog type negative feedback is effected.

Abstract: A polar leapfrog filter includes at least one polar network. The polar network comprises a differentiator constituted by an operational amplifier having input and output terminals, and a first integrator formed by a first capacitor for providing negative feedback to the operational amplifier and a first variable transconductance amplifier; and a second integrator formed by a second capacitor for providing negative feedback to the first integrator, and a second variable transconductance amplifier. An integrator is provided at each of the input and output stages, and a third integrator is provided immediately preceding the output side integrator. In the case where two or more said polar networks are incorporated, an additional integrator is provided between the polar networks. The total number of all the circuits is selected to be even and equal to the order of the filter.

Abstract: An all-pass filter includes an adder which comprises a variable conductance amplifier and a capacitor connected to the output terminal thereof. The adder is being arranged to add the output of a band pass filter and an input signal together.

Abstract: An semiconductor junction capacitance element equipped with the function of preventing electrostatic breakdown is disclosed in which a main PN junction adapted to serve as variable capacitance diode is defined in an epitaxial layer of a first conductivity type. A diffusion layer of the first conductivity type is provided in the epitaxial layer at a position spaced apart from a lateral PN junction which is exposed at major surface of the epitaxial layer so that the breakdown voltage of the lateral PN junction is set up to be lower than the breakdown voltage of the main PN junction by virtue of the provision of the diffusion layer.

Abstract: A variable time-constant differentiator comprises an operational amplifier t which a signal is inputted through a capacitor; and a variable transconductance amplifier connected between an input terminal to which a signal is applied and an 5 output terminal.

Abstract: A polar leapfrog filter includes at least one polar network. The polar network comprises a differentiator constituted by an operational amplifier having input and output terminals, and a first integrator formed by a first capacitor for providing negative feedback to the operational amplifier and a first variable transconductance amplifier; and a second integrator formed by a second capacitor for providing negative feedback to the first integrator, and a second variable transconductance amplifier. A differentiator is provided at each of the input and output stages of the filter. In the case where two or more said polar networks are incorporated, an additional differentiator is provided between the polar networks. The total number of all the circuit units constituting the filter is selected to provide odd order and equal order for the filter. The circuit units are connected in such a manner that leapfrog type negative feedback is effected.

Abstract: An active filter circuit comprises a differentiator constituted by an operational amplifier having an input terminal and output terminal, and a first integrator constituted by a first capacitor and a first variable conductance amplifier for providing negative feedback to the operational amplifier and a first variable conductance amplifier; and a second integrator constituted by a second capacitor and a second variable conductance amplifier for providing negative feedback to the first integrator. The active filter circuit is arranged such that a damping pole is set up at a predetermined frequency by adjusting operating currents of the first and second variable conductance amplifiers.

Abstract: A waveform shaping circuit is provided which comprises a first and a second integrating circuit to which is applied an input signal having digital data mingled therein; and a differential amplifier having a first input terminal to which the input terminal is applied and a second input terminal to which integrated output derived from the first integrating circuit. The second integrating circuit has its time constant set up to be lower than that of the first integrating circuit; and the first integrating circuit has a capacitor intermittently charged with output derived from the second integrating circuit, so that the input signal is converted to digital data.

Abstract: A leapfrog filter comprises a first integrator made up of a first operational amplifier and a first capacitor connected to output terminal of the first operational amplifier; a second integrator made up of a second operational amplifier and a second capacitor connected to inverting input terminal and output terminal of the second operational amplifier; and a variable current source circuit. The first operational amplifier has the output terminal thereof connected to non-inverting input terminal of the second operational amplifier. The second operational amplifier has the output terminal thereof connected to inverting input terminal of the first operational amplifier. An input terminal is connected to non-inverting input terminal of the first operational amplifier; and output terminal connected to the output terminal of the second operational amplifier.

Abstract: In a tuning circuit, use is made of a current-controlled type variable inductor comprising a tuning coil and a control coil for controlling the magnetic flux density of the tuning coil. The tuning coil is connected in series with the antenna; a tuning capacitor is connected to each end of tuning coil; and by controlling a current flowing through the control coil, magnetic flux induced in the tuning coil is increased, decreased or cancelled so that the magnetic flux density of the tuning coil is adjusted to control the inductance thereof, thereby permitting the tuning circuit to be tuned to any desired frequency in the receiving frequency band.

Abstract: A leapfrog filter comprising a first and a second integrator each consisting of an operational amplifier and integrating capacitor. The leapfrog filter includes differential amplifier which is arranged to differentially supply current to the first and second integrators through a first and a second current source circuit respectively; and a third current source circuit for adjusting the sum of currents supplied to the first and second current source circuits, wherein characteristics such as the center frequency f.sub.o and quality factor Q of the leapfrog filter are controlled by adjusting the respective current values.

Abstract: A variable-capacitance diode element is disclosed which comprises a semiconductor substrate of a first conductivity type having an epitaxial layer of the first conductivity type provided on a main surface portion thereof, said epitaxial layer having a higher resistivity than that of said semiconductor substrate; a first diffusion layer of the first conductivity type diffused in said epitaxial layer and having a lower resistivity than that of said epitaxial layer; a second diffusion layer of a second conductivity type surrounded by said first diffusion layer and having a lower resistivity than that of said first diffusion layer; and a third diffusion layer of the second conductivity type of a small diffusion length covering an exposed portion of a major surface of said first diffusion layer and an exposed portion of a major surface of said second diffusion layer. With such construction, the capacitance variation range of the diode element is widened, and the high-frequency serial resistance R.sub.