Hitachi, Ltd.

Hitachi Tohbu Semiconductor, Ltd.

Yuko Tamba

Takao Okazaki

Kazuo Yamakido

Yukihito Ishihara

Katsuhiro Furukawa

Norimitsu Nishikawa

Yoichiro Kobayashi

Masanori Otsuka

Akihiro Nagatani

Taiji Kondou

Digital demodulators for phase modulated and amplitude-phase modulated

In a semiconductor integrated circuit having a plurality of electronic circuits each provided with interfaces used for effecting signal transmission, and supplied with operating voltages from a plurality of independent power supply terminals, protective elements each having high threshold voltages at which the elements are off in the ordinary state of power supply are provided, and a resistor and a diode both for preventing electrostatic breakdown are connected to the gate of an input MOSFET of the interface for carrying out signal transmission between the electronic circuits. Even when a high voltage due to static electricity is applied to each power supply terminal while the semiconductor integrated circuit is handled, electrostatic breakdown of the interface can be prevented by the protective element or the electrostatic breakdown preventive circuit comprising a resistor and a diode.

Semiconductor integrated circuit

A Gm-controllable amplifier is used in an OTA-C filter. Specifically, the amplifier is one in which a constant voltage from a bias circuit is applied to the gates of load MOSFETs connected to the drains of input differential MOSFETs of a differential amplifier to allow the load MOSFETs to operate as constant current sources and the inverted output terminals of the circuit are connected to the input terminals. The load MOSFETs of the input differential MOSFETs are made to operate as the constant current sources, so that the drain voltages of the input differential MOSFETs become independent of the threshold voltage of the load MOSFETs. Even if the supply voltage is set to as low as about 1.5 V, the input differential MOSFETs can be prevented from being unsaturated when the input signals rise. Since the inverted output terminals are coupled to the input terminals, the currents outputted from the inverted output terminals in the opposite direction of the current coming from the non-inverted output terminals can be absorbed from the non-inverting input terminals, so that the balance of the circuit can be easily maintained.

Analog filter circuit and semiconductor integrated circuit device using

The number of current sources and switches necessary for a plurality of unit D/A converters using equal reference currents, are drastically reduced to reduce the parasitic capacitance coupled to current output lines, by converting a plurality of digital signals of a predetermined bit, which are divided from an input digital signal, into an analog current unit D/A converters and by converting the analog current in a manner to correspond to the weights of the corresponding input digital signals, thereby to synthesize the currents. The fixed reference digital signal is inputted to the D/A converter for cancelling offsets. The offsets of a plurality of analog output signals in positive and opposite phases obtained by branching the output of the D/A converter are individually detected. After this, the DC offset values of the individual analog outputs are used as offset adjusted negative feedback signals for a desired value. One of them is the digital signal to be fed back to the input portion of the D/A converter whereas the other is the analog signal to be fed to a path portion obtained by branching the output of the D/A converter.

Converter, offset adjustor, and portable communication terminal unit

The difference between the output current of a voltage-current converter circuit and the output current of a local D/A converter circuit 2, whose output current is controlled by a feedback signal, is integrated by an analog circuit of which one end is connected to a DC potential point, and the voltage obtained by the integration thereof is quantized by a quantizing circuit. The result is integrated by a digital integrating circuit and is fed to a feedback correcting circuit 6 and, further, the result of A/D conversion is output. The feedback correcting circuit outputs a temporary feedback signal while the digital integration is being operated based on the output of the quantizing circuit. After the digital integrating operation completes the digital integration operation, a corrected feedback signal is generated instead of the temporary feedback signal. The signals inputted into the analog circuit 3 are continuously sampled even while the digital integration operation is being carried out.

Analog/digital converter of the over-sampling type with feedback

An over-sampling analog-to-digital converter using a current switching circuit 102 as a local digital-to-analog converter, wherein a difference between the output currents Isig and Iq of a voltage-to-current converter circuit 101 and a current switching circuit is integrated by a capacitor 105 of which the one end is grounded to a dc potential VB. Further, the current switching circuit 102 has many bits to decrease the difference current between the signal current Isig and the feedback current signal Iq. Moreover, the level-shifting function of the voltage-to-current converter circuit 101 makes it possible to apparently subtract the dc component from the input analog signal Vsig which is produced based on an internally generated dc voltage as a dc bias voltage, and to decrease a change in the voltage between the electrodes of a capacitor caused by the integration of current.

Growing community of inventors

Ohme, Japan

Yuko Tamba