Sharp Kabushiki Kaisha Corporation

Sharp Corporation

Keiichi Sakuno

Naoyasu Iketani

John Kevin Twynam

Hiroshi Itoh

Masato Sasaki

Hiroshi Kawamura

Yoshiaki Nozaki

Takao Hasegawa

Tomohiro Nozawa

Toshiyuki Oka

A power transmission device is provided that enables more accurate detection of an undesired switching state for a switching element and an appropriate supply of power. The power transmission device includes a power supply, a switching element, a ringing detection circuit, and a control circuit unit. The ringing detection circuit detects ringing that occurs in the switching element. The control circuit unit controls at least the power supply or the switching element in accordance with a detection result of the ringing detection circuit. The ringing detection circuit includes a diode and a resistor. The diode conducts when a negative polarity voltage is generated in the switching element. The resistor is connected in series with the diode.

Power transmission device and contactless power transmission device

In a switching power supply circuit of the invention, a low-voltage node capacitor is connected between a primary-side low-voltage stable potential node and a secondary-side low-voltage stable potential node, and a high-voltage node capacitor is connected between a primary-side high-voltage stable potential node and an anode of a rectifier element. Thereby, it is possible to provide the switching power supply circuit which achieves, with a simple configuration, both of noise reduction and potential stabilization of stable potential nodes.

Switching power supply circuit with reduced noise and potential stabilization of stable potential nodes

This composite semiconductor device has a normally-on first field effect transistor and a normally-off second field effect transistor connected in series between first and second terminals, gates of the first and second field effect transistors being connected to second and third terminals, respectively, and N diodes being connected in series in a forward direction between a drain and a source of the second field effect transistor. Therefore, a drain-source voltage (Vds) of the second field effect transistor can be restricted to a voltage not higher than a withstand voltage of the second field effect transistor.

Composite semiconductor device

A power amplification circuit, and a communication device using the same, which are capable of suppressing gain decreases of a power amplifier due to increases in input signal power in a state near the saturation operation, capable of reducing its size, and low in distortion and high in efficiency. The power amplification circuit includes a power amplifier and a negative feedback circuit connected between a signal input terminal and a signal output terminal of the power amplifier. Impedance of the negative feedback circuit depends on a signal voltage occurring across the negative feedback circuit. By adjusting the characteristic that the negative feedback quantity of the negative feedback circuit to the power amplifier is variable depending on input signal power, gain fluctuations of the power amplifier due to increases or decreases of input signal power or output signal power around a specified output signal power are suppressed.

Power amplification circuit and communication device using the same

A resistor and a capacitor are provided for a variable impedance element which performs distortion compensation of a power amplifier. Thus, compensation of amplitude-amplitude distortion and amplitude-phase distortion can be separately adjusted. As a result, distortion of the power amplifier can be reduced effectively and a highly efficient operation is made possible.

Power amplifier and communication device including power amplifier

A power amplifier has a front and a rear stage. In the rear stage, to a base of a signal-amplifying bipolar transistor is connected one end of a variable impedance element whose impedance changes according to an input power level. An adjusting circuit is connected between the other end of the variable impedance element and a ground. A DC current adjusting element is connected between the other end of the variable impedance element and a supply voltage terminal. The front stage is made to perform class A operation or class AB operation near class A operation, while the rear stage is made to perform class B operation or class AB operation near class B operation. The distortion characteristic of the rear stage is adjusted by the variable impedance element, the adjusting circuit, and the DC current adjusting element so as to offset the distortion characteristic of the front stage.

Power amplifier and radio communication apparatus using the same

In a transistor power amplifier, a base of a power amplifying bipolar transistor is connected with a gain control power source via a bias resistor. The power amplifying transistor is directly biased from the gain control power source via the bias resistor, and not via a base driving bipolar transistor so as to widen an effective gain control voltage range by an amount corresponding to an ON-state voltage across a base and emitter of the base driving bipolar transistor.

Growing community of inventors

Nara, Japan

Keiichi Sakuno