Abstract: An operational amplifier with a broad applicable band and little disturbing noise which is capable of preventing oscillation even when used in connection with a negative feedback path. The operational amplifier amplifies a difference between two input voltage signals to a non-inverting input terminal and an inverting input terminal and outputs the amplified difference to an output terminal. The operational amplifier includes an input voltage/current conversion stage which outputs, to the non-inverting input terminal and the inverting input terminal, a current signal having a difference current component in accordance with the difference between the two input voltage signals; a current amplification stage which performs current amplification on the current signal outputted from the input voltage/current conversion stage; and an output buffer stage which converts, into a voltage signal, the output current signal from the current amplification stage and applies the voltage signal to the output terminal.

Abstract: For reducing various adverse effects due to provision of a low-pass filter, while suppressing an oscillation generated therein, there is provide a feedback circuit, having at least one operational amplifier, having a low-pass filter in an output portion thereof, for feeding a signal from the output portion back thereto, including: a first feedback circuit portion for negatively feeding a signal from an input terminal of the low-pass filter back to an inverted input terminal of the operational amplifier; and a second feedback circuit portion for negatively feeding a signal from an output terminal of the low-pass filter back to the inverted input terminal of the operational amplifier.

Abstract: There is provided an operational amplifier with a broad applicable band and little disturbing noise which is capable of preventing oscillation even when used in connection with a negative feedback path. The present invention relates to an operational amplifier which amplifies a difference between two input voltage signals to a non-inverting input terminal and an inverting input terminal and outputs the amplified difference to an output terminal.

Abstract: A protection circuit, for protecting a protection target circuit from over-current flowing therein without stopping supply of electricpower thereto, includes: a current detecting portion for detecting current flowing in the protection target circuit in form of voltage thereof; a comparing portion for comparing the voltage detected within the current detection portion, or a difference between the detected voltage and input voltage into the protection target circuit, with a reference voltage, thereby to output a comparison result; and a clipping portion for clipping input voltage direct to the protection target circuit, or voltage before being amplified to be input voltage into the protection target circuit by amplification, when the comparison result indicates that current flowing through the protection target circuit is over-current.

Abstract: A push-pull switching power converter includes, between high and low output terminals of a DC power source, a series circuit having a first switching device, a primary winding of a first transformer, a primary winding of a second transformer, and a second switching device in this order, and a series circuit composed of two capacitors, as well as a partial path for current resonance. The partial path connects middle points of the two series circuits. Voltage resonance causes the waveform of a switching voltage, which corresponds to the difference in voltages between high potential terminal of a primary of the first transformer and low potential terminal of a primary of the second transformer, to be a sine wave. Current resonance causes the waveform of a switching current, which corresponds to a combined current of primary winding currents of the first transformer and the second transformer, to be a sine wave.

Abstract: A small-sized, highly efficient power conversion apparatus is provided which is capable of stabilizing its output and which can be easily applied to parallel driving. The power conversion apparatus turns on and off paired switching elements, lets an alternating current flow through a primary winding of a transformer, rectifies and smoothes an AC voltage thus induced across a secondary winding, thereby obtaining a DC output. On the basis of a rectangular wave signal having a duty ratio of 50% formed by a rectangular wave oscillator means, a dead time generator generates complementary on/off control signals having a dead time and supplies the on/off control signals to the paired switching elements.

Abstract: For reducing various adverse effects due to provision of a low-pass filter, while suppressing an oscillation generated therein, there is provide a feedback circuit, having at least one operational amplifier, having a low-pass filter in an output portion thereof, for feeding a signal from the output portion back thereto, including: a first feedback circuit portion for negatively feeding a signal from an input terminal of the low-pass filter back to an inverted input terminal of the operational amplifier; and a second feedback circuit portion for negatively feeding a signal from an output terminal of the low-pass filter back to the inverted input terminal of the operational amplifier.

Abstract: To provide a switching circuit and a digital power amplifier capable of supplying much power to a load, as compared with a conventional circuit. A switching circuit of the present invention comprises a plurality of switching circuit units, in which first to fourth switching elements are connected in a loop in this order, having a DC power source, one end of which is connected to a node between the first and fourth switching elements, and the other end of which is connected to a node between the second and third switching elements. The plurality of switching circuit units are cascade-connected, with one of the external connection terminals of the switching circuit unit on the first stage being connected to one terminal of the load, and with the other of the external connection terminals of the switching circuit unit on the last stage being connected to the other terminal of the load.

Abstract: A push-pull switching power converter includes, between high and low output terminals of a DC power source, a series circuit having a first switching device, a primary winding of a first transformer, a primary winding of a second transformer, and a second switching device in this order, and a series circuit composed of two capacitors, as well as a partial path for current resonance. The partial path connects middle points of the two series circuits. Voltage resonance causes the waveform of a switching voltage, which corresponds to the difference in voltages between high potential terminal of a primary of the first transformer and low potential terminal of a primary of the second transformer, to be a sine wave. Current resonance causes the waveform of a switching current, which corresponds to a combined current of primary winding currents of the first transformer and the second transformer, to be a sine wave.

Abstract: A digital power amplifier has first and second switches, between a high potential power line and a low potential power line, which operate complementarily. When switching an ON switch, dead time is provided to control power to a low-pass filter. In a switching section, the first switch, a first coil, a second coil and the second switch are connected in series, between the high and low potential power lines. The switching section includes a first high-speed diode having a cathode connected to the high potential power line and an anode connected to a node between the second coil and the second switch, and a second high-speed, diode having a cathode connected to a node between the first switch and the first coil and an anode connected to the low potential power line. The node between the first coil and the second coil is connected to the low-pass filter side.

Abstract: To provide a switching circuit and a digital power amplifier capable of supplying much power to a load, as compared with a conventional circuit.

Abstract: A digital power amplifier has a reduced size, high output, high efficiency and low power consumption. Electrical isolation is provided between input and output sections by a photo-coupler on a transmission passage for turning into a digital signal.

Abstract: To provide a digital power amplifier having high power amplification efficiency.

Abstract: A digital power amplifier has a reduced size, high output, high efficiency and low power consumption. Electrical isolation is provided between input and output sections by a photo-coupler on a transmission passage for turning into a digital signal.