Fujitsu Corporation

Yoshinori Yoshikawa

Kunihiko Gotoh

Atsushi Matsuda

Yuji Segawa

Hiromi Nanba

Masaru Otsuka

Tohru Mizutani

Masashi Okubo

Kenichi Minobe

Akira Haga

Atsushi Hitaka

Osamu Kikuchi

An integrated circuit includes an analog signal output unit which converts a digital output signal into at least one analog output signal, and outputs the at least one analog output signal, an analog signal input unit which converts at least one analog input signal received from an exterior into a digital input signal, a switch circuit which provides at least one signal path through which the at least one analog output signal is supplied from the analog signal output unit to the analog signal input unit as the at least one analog input signal, and an offset adjustment control circuit which supplies an output offset from the analog signal output unit to the analog signal input unit via the at least one signal path so as to detect the digital input signal inclusive of the output offset and an input offset, and cancels offsets of the analog signal output unit and the analog signal input unit in response to the output offset and the input offset obtained from the detected digital input signal.

Digital-analog-conversion circuit having function of automatic offset adjustment

The inverter functioning as a comparator, dummy inverter having the same electric characteristics as the inverter, and control circuit are provided. Vth detecting input voltage output from the control circuit is input into the dummy inverter, Vth detecting output voltage output from the dummy inverter is input into the control circuit, and the threshold voltage of the dummy inverter is detected. The threshold voltage of the inverter is controlled by controlling the back gate voltages of the MOS transistors of the dummy inverter and the inverter in such a manner that the threshold voltage of the dummy inverter coincide with an external reference voltage.

Comparator and voltage controlled oscillator circuit

A constant current source circuit includes a current mirror circuit supplying a load circuit with an output current which is regulated on the basis of a reference current, a transistor having an emitter, a collector connected to a first power source line, and a base coupled to the current mirror circuit, and a resistor coupled between the emitter and base. The reference current passes through the resistor. A current control circuit controls a current directed to a second power source line in accordance with a bias voltage. The above current consists of the reference current and a collector current passing through the transistor. A bias circuit having a current path derives the bias voltage from a current passing from the first power source line to the second power source line through the current path.

Constant current source circuit

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Kawasaki, Japan

Yoshinori Yoshikawa