Abstract: A contactless IC card includes a reference voltage circuit, a judging circuit for monitoring a reference voltage that is outputted from the reference voltage circuit, and a power supply stabilization, unit. The judging circuit judges whether the reference voltage is equal to or higher than a predetermined voltage. When the reference voltage does not reach the predetermined voltage, the power supply stabilization unit supplies energy to the power supply to suppress a steep increase in the power supply voltage, thereby stabilizing the power supply in the contactless IC card and suppressing deterioration of the signal quality.

Abstract: A pseudo-image signal producing section produces a pseudo-image signal imitating an actual image signal. An amplitude detection section detects the amplitude of the pseudo-image signal having passed through a complex filter circuit. A filter control section controls an element value control section in the complex filter circuit so as to decrease the detected amplitude. The element value control section performs an element value adjustment so that absolute element values of a pair of elements corresponding to each other in two filter circuits in the complex filter circuit increase/decrease in opposite directions.

Abstract: The present invention provides a contactless IC card including a reference voltage circuit, a judging circuit for monitoring a reference voltage that is outputted from the reference voltage circuit, and a power supply stabilization means, thereby judging whether the reference voltage is equal to or higher than a predetermined voltage using the judging circuit. When the reference voltage does not reach the predetermined voltage, the power supply stabilization means supplies energy to the power supply to suppress a steep increase in the power supply voltage, thereby stabilizing the power supply in the IC and suppressing deterioration of the signal quality.

Abstract: A variable gain amplification circuit comprises a signal generator that has an output terminal and is able to vary an output amplitude; a variable capacitor connected between the output terminal and an AC grounded terminal; and a control circuit for controlling the output amplitude of the signal generator, and a capacitance of the variable capacitor. Therefore, unnecessary signals can be attenuated even when the gain is low, and degradation in distortion characteristics in the latter block can be suppressed.

Abstract: A power supply circuit of the present invention includes: a current detection circuit connected between a first power supply voltage section for applying a first power supply voltage to a first electronic circuit and a second power supply voltage section for applying a second power supply voltage to a second electronic circuit, the current detection circuit having a monitor terminal for monitoring a current flowing from the first power supply voltage section to the second power supply voltage section; and a current compensation circuit connected to the first power supply voltage section and the monitor terminal, the current compensation circuit controlling a compensation current flowing from the first power supply voltage section to a ground based on the monitored current to compensate for current fluctuations caused by load fluctuations of the second electronic circuit.

Abstract: A power supply circuit of the present invention includes: a current detection circuit connected between a first power supply voltage section for applying a first power supply voltage to a first electronic circuit and a second power supply voltage section for applying a second power supply voltage to a second electronic circuit, the current detection circuit having a monitor terminal for monitoring a current flowing from the first power supply voltage section to the second power supply voltage section; and a current compensation circuit connected to the first power supply voltage section and the monitor terminal, the current compensation circuit controlling a compensation current flowing from the first power supply voltage section to a ground based on the monitored current to compensate for current fluctuations caused by load fluctuations of the second electronic circuit.

Abstract: The present invention has an objective of providing a semiconductor amplifier circuit having a cascode amplifier in which a negative characteristic of an output conductance is improved at least in a particular frequency band. A semiconductor amplifier 1 includes a cascode amplifier 500 having a transistor 101 and a transistor 102 which are cascaded, and improvement means for improving the negative characteristic of the output conductance Gout of the cascode amplifier 500 at least in a particular frequency band.

Abstract: In an active area surrounded with an isolation formed on a silicon substrate, a large number of unit cells are disposed in a matrix, and the unit cell together form one MOSFET. Each of the unit includes a ring gate electrode in the shape of a regular octagon, a drain region and a source region formed at the inside and outside of the gate electrode, respectively, two gate withdrawn wires extending from the gate electrode to area above the isolation, a substrate contact portion in which the surface of the substrate is exposed, and contacts for electrically connecting these elements with wires. These elements such as the ring gate electrode and the gate withdrawn wires are formed so as to attain a high frequency characteristic as good as possible. Thus a MOSFET for use in a high frequency signal device, the high frequency characteristic such as the minimum noise figure and the maximum oscillation frequency in particular can be totally improved.