Matsushita Electric Industrial Co., Ltd.

Yuichi Tateyama

Hisato Takeuchi

Takashi Otsuka

Junichi Matsuura

Takaharu Saeki

Shuji Shibuya

Shigeo Masai

To provide a MOS varactor in which oscillation frequency variation is small and variation in a capacitance changing voltage is small, and a voltage-controlled oscillator using the MOS varactor, as a load capacitor of an oscillating circuit composed of a feedback resistor, an amplifier, and a crystal vibrator, a variable electrostatic capacitor, which is generated between drain/source terminals and a gate terminal of each of MOS transistorsandeach of which source and drain terminals are short-circuited, is connected. A bulk terminal of each of the MOS transistorsandis connected to one terminal of a resistor, a voltage is applied to the other terminal of the resistor, the bulk terminal of each of the MOS transistorsandis connected to one terminal of a capacitor, and the other terminal of the capacitoris grounded.

MOS varactor and voltage-controlled oscillator using the same

It is an object of the invention to obtain a stable operation with a low phase noise. Moreover, it is another object to obtain an oscillating output which does not cause the delay of a starting time. According to the invention, it is possible to implement a crystal oscillating circuit capable of superposing a signal obtained by feeding back the oscillating output of a crystal oscillating member () by a feedback circuit () on a control signal for selecting the load capacity of a load capacity selecting portion (), and influencing an MOS transistor () by the voltage noise of the control signal with difficulty, thereby reducing a phase noise, and furthermore, limiting a control signal to be input to the load capacity selecting portion () for a certain time in starting and carrying out the starting in a short time.

Crystal oscillation circuit with frequency regulation

An oscillator circuit configured by a feedback resistance, an amplifierand a quartz vibratorhas a load resistance. MOS transistorsshort-circuited at source and drain terminals has a capacitance, as a variable capacitance, occurring at between the source-drain terminal and gate terminal. A series connection of DC-cut capacitanceand variable capacitance (MOS transistor) is configured between one and the other terminals of the quartz vibratorand an AC ground terminal. For example, a threshold voltage control signal for MOS transistoris inputted to the source-drain terminal through a high-frequency removing circuit. Meanwhile, a signal that a temperature compensation control signal and an external voltage frequency control signal are superimposed together is inputted to the gate terminal. This makes it possible to desirably determine an output bias to a temperature compensation control circuit and an external voltage frequency control circuit.

Voltage-controlled oscillator

A compact semiconductor device forming a capacitive element for high frequencies that allows good capacitance change to be achieved is provided. AMOS capacitor type semiconductor device includes a gate electrode formed on a surface of a substrate through a gate insulating film, source/drain regions provided to have the gate electrode therebetween, and a back gate including a contact diffusion region for contacting the substrate. Voltage applied across the regions between the source or drain region and the gate electrode and between the gate electrode and the back gate is adjusted, so that charge accumulated at the gate insulating film can be adjusted. In the device, the distance between the source and drain regions or the distance between the back gate and the gate electrode is determined so that electrons or holes can be accumulated at the interface between the gate insulating film and the substrate within a cycle of the applied voltage.

MOS capacitor type semiconductor device and crystal oscillation device using the same

An N type semiconductor layer is epitaxially grown on a P type semiconductor substrate of which one end is grounded, and an element isolation layer made of a P type diffusion layer is formed by means of diffusion around the N type semiconductor layer in order to electrically isolate the N type semiconductor layer. The metal layer which is located above the N type semiconductor layer and which forms a wire or a bonding pad is isolated from the N type semiconductor layer in which a diffusion layer or the like has been formed by an insulating film. An N type buried diffusion layer having an impurity concentration higher than that of the N type semiconductor layer is provided between the P type semiconductor substrate and the N type semiconductor layer. In addition, a P type semiconductor layer is formed by means of diffusion between the insulating film and the N type semiconductor layer plus the element isolation layer.

Semiconductor device

A temperature compensating crystal oscillation device includes a constant voltage circuit (,) for outputting a predetermined voltage independent of the ambient temperature, a temperature sensor circuit (,) for outputting a voltage in proportion to the ambient temperature, and a control circuit (,) for receiving the constant voltage output from the constant voltage circuit (,) and the voltage output in proportion to the temperature from the temperature sensor circuit (,) and for generating a control voltage (Vc) used for compensating a temperature characteristic of a quartz oscillator in the entire range of the ambient temperature through polygonal lines approximation of a negative cubic curve by using continuous lines. Furthermore, the crystal oscillation device includes a VCXO (,) whose oscillation frequency is controlled to be a predetermined value by the control voltage (Vc), and a ROM/RAM circuit (,) for storing temperature compensating parameters used for compensation of a temperature characteristic of the control voltage (Vc) for optimizing the oscillation frequency of the VCXO (,).

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Sagamihara, Japan

Yuichi Tateyama