Fujitsu Corporation

Fujitsu Semiconductor Limited

Takahiro Watai

Masaya Mizutani

Koji Takekawa

Koju Aoki

Hiroyuki Sakima

Hirokazu Tanaka

Tetsuji Funaki

Takuya Okajima

Tatsuo Kumano

Kunihiko Gotoh

Katsuya Shimizu

Tetsuo Yagyu

A method and circuit for preventing an output signal, which has been corrected through digital correction or analog correction, from deviating from a target value and for preventing power supply noise and power consumption from increasing. A sensor amplification circuit receives output of a sensor as an input signal. Correction points are set at predetermined temperature intervals. The sensor amplification circuit performs digital correction for correcting the input signal with correction data set for each correction point. Further, the sensor amplification circuit performs a second correction for correcting the input signal between the correction points with gradient data calculated from the correction data for two of the correction points that are adjacent to each other.

Method and circuit for correcting sensor temperature dependency characteristic

One aspect of the embodiments relates to a programmable gain circuit including an amplification unit amplifying an input signal, an input resistor coupled to an input terminal of the amplification unit, a feedback resistor coupled between an output terminal of the amplification unit and the input terminal of the amplification unit, a first switch switching a resistance value of the feedback resistor, a second switch switching a resistance value of the input resistor, and a control unit controlling the second switch such that the second switch switches the resistance value of the input resistor when the first switch switches the resistance value of the feedback resistor.

Programmable gain circuit and amplification circuit

An amplifier circuit which is connected to a sensor and variably sets an amplification property and a control method thereof are disclosed, the circuit having the capability of restricting the influence of change with time and temperature change. The amplifier circuit, which receives, as an input, a detection signal from the sensor and variably sets an amplification property, comprises: (1) a first reference value retaining unitfor retaining a first reference value Kfor setting an amplification property which makes an output signal be a specified detection reference output voltage when a reference input condition KJ is detected; (2) a correction signal generation unitfor generating a correction signal HS which reduces the difference between an amplification property actual measurement value and an amplification property set value; and (3) a first amplification property correction unitfor correcting the first reference value Kbased on the correction signal HS.

Amplifier circuit and control method thereof

This invention provides a comparator circuit which outputs a stable waveform without oscillation even if a gradient of a change of a comparison input signal is small and determines a magnitude of the comparison input signal within a predetermined threshold value regardless of the increase/decrease direction of the comparison input signal. A comparator circuitcomprises a capacitative elementwhich is charged or discharged corresponding to a difference of potential between a comparison input signal IN and a reference input signal REF, an analog buffer portionwhich outputs high level if the voltage is above a threshold voltage Vth and low level if it is less than the threshold voltage Vth, an edge detecting portionwhich detects leading and trailing edges of the analog buffer portionso as to output an up signal UP and a down signal DOWN and a charge pump portionwhich charges a capacitative portion corresponding to the up signal UP and discharges the capacitative portion corresponding to the down signal DOWN.

Comparator circuit and control method thereof

Provided are two monitor circuits for monitoring two input signals of an input stage differential amplifier, respectively, and two monitor circuit for monitoring two output signals of the input stage differential amplifier, respectively. When failure occurs at the bridge circuit of a sensor element or at the input stage differential amplifier, the monitoring units or the monitoring units detect abnormality, which makes it possible to detect the failure of the sensor element or the input stage differential amplifier. Therefore it is possible to detect failure such as a disconnection or a short circuit of the bridge circuit of the sensor element and failure which has occurred at the amplifier for amplifying outputs of the sensor element.

Sensor detection apparatus and sensor

A ringtrip judging circuit includes a single comparator for comparing a detection value of a ringing current with a threshold value and for outputting the result of the comparison, a threshold value control circuit for supplying the threshold value to the comparator, and a judging circuit for judging ringtrip based on the output of the comparator. During a prescribed period after ringing signal transmission, the threshold value control circuit changes the threshold value in a steplike manner in accordance with the result of the comparison, thereby determining a threshold value greater than a peak value during the prescribed period, and based on it, determines a threshold value for ringtrip judgement and supplies it to the comparator.

Ringtrip judging circuit

An output circuit, for minimizing output idle current fluctuations and improve the output voltage range, has first and second transistors connected to first and second power sources, with a plurality of diodes connected to control terminals of the first and second transistors. The output circuit further includes a third transistor having a first terminal connected to the second power source and a second terminal connected to a predetermined position among the plurality of diodes. A predetermined voltage is applied from the diodes to the control terminal of the first transistor when the third transistor is saturated, to bring a level of an output of said output circuit close to a level of the second power source. A fourth transistor, a fifth transistor, a first resistor, and a capacitor are also provided. The forth transistor has a control terminal connected to an output of a differential circuit, and a first terminal connected to the second power source through the first resistor as well as to the control terminals of the third and fifth transistors. A second terminal is connected to the first power source, with the fifth transistor having a first terminal connected to the second power source and a second terminal connected to the control terminal of the second transistor. The capacitor is connected between the control terminal of the fourth transistor and the second terminal of the fifth transistor. This output circuit also limits the output voltage without changing the impedance of the high-impedance input.

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Kasugai, Japan

Takahiro Watai