Panasonic Corporation

Socionext Inc.

Shinichiro Uemura

Atsushi Ohara

Takafumi Nasu

Hisashi Adachi

Takayuki Kai

Yukio Hiraoka

Takahito Miyazaki

A variable gain transconductance amplifier includes an amplifier transistor connected to an input node, a cascode transistor having a source connected to a drain of the amplifier transistor and having a drain connected to an output node, and a switching circuit connecting or disconnecting a node to which the amplifier transistor and the cascode transistor are connected to or from a fixed potential in a switchable manner. A variable gain circuit may include the variable gain transconductance amplifier.

Variable gain circuit and tuner system provided with same

A parallel resonant circuit with excellent distortion and saturation characteristics is provided at low power consumption. A first power-supply voltage is applied to the parallel resonant circuit. In the parallel resonant circuit, a variable resistor includes one or more parallel-connected branches. Each of the branches includes a series circuit of a resistor and a MOS switch. A second power supply supplies power of control signals applied to respective gates of the MOS switches, and supplies back gate voltages to the MOS switches. A power-supply voltage of the second power supply is higher than the first power-supply voltage.

Parallel resonant circuit

A digital circuit portion () and an analog circuit portion () are formed in a surface portion of a semiconductor substrate (). A via () is formed in a region between the digital circuit portion () and the analog circuit portion (). The via () extends through the semiconductor substrate () from a front surface to a back surface thereof, and is made of a dielectric () having its surface covered by a metal (). The metal () is grounded. Signal interference between the analog circuit portion () and the digital circuit portion () is reduced by the via ().

Semiconductor device

A frequency synthesizer includes a digitally-controlled oscillator and an oscillation frequency control unit. The digitally-controlled oscillator includes a loop-shaped transmission line path having an odd number of parallel portions in each of which two conductors are arranged in parallel to each other with a space therebetween, and an odd number of intersection portions in each of which two conductors intersect spatially, an active circuit coupled between the two conductors, and a first variable capacitance unit and a second variable capacitance unit. The oscillation frequency control unit includes a &#x3a3;&#x394; modulation circuit for subjecting to &#x3a3;&#x394; modulation a first control signal for switching a high capacitance state and a low capacitance state of a first variable capacitance element included in the first variable capacitance unit.

Digitally-controlled oscillator, frequency synthesizer and radio communication device

A semiconductor device includes a layered region () formed in a semiconductor substrate () of a first conductivity type, and an electrode pad () formed on the semiconductor substrate with an interlayer insulating film () interposed therebetween and placed above the layered region. The layered region includes a first impurity diffusion region (), a second impurity diffusion region () formed on the first impurity diffusion region, and a third impurity diffusion region () formed on the first impurity diffusion region and surrounding a periphery of the second impurity diffusion region. a conductivity type of the first impurity diffusion region and a conductivity type of the third impurity diffusion region are a second conductivity type, and a conductivity type of the second impurity diffusion region is the first conductivity type. An impurity concentration of the third impurity diffusion region is higher than an impurity concentration of the first impurity diffusion region, and the third impurity diffusion region is electrically connected to a terminal fixed to a constant potential.

Growing community of inventors

Osaka, Japan

Shinichiro Uemura