Rohm Co., Ltd.

Hiroyuki Makimoto

Yuki Inoue

Yusuke Yoshii

Ayumu Kambara

An operational amplifiercomprises transistors Qand Qforming an input stage, and input resistors Rand Rwhich form a filter together with parasitic capacitors Cand Caccompanying the transistors Qand Q. Resistance values R of the resistors Rand Rmay be set to R=1/(2&#x3c0;&#xb7;fc&#xb7;C), where C is the capacitance value of each of the parasitic capacitors Cand C, and fc is the target cutoff frequency of the filter. The operational amplifiermay also include a power supply resistor Rwhich forms a filter together with a parasitic capacitor Caccompanying a power supply line.

Operational amplifier

A voltage monitoring circuit monitors a magnitude relationship between a monitoring target voltage and a determination voltage and is capable of suppressing the influence of an offset of a reference voltage upon the determination voltage and setting the determination voltage as desired. The voltage monitoring circuit includes: an input terminal, applied with a monitoring target voltage or a divided voltage of the monitoring target voltage; a reference voltage generating circuit, generating a first reference voltage; a linear power circuit, converting the first reference voltage to a second reference voltage; a feedback resistor, generating a divided voltage of the second reference voltage, and negatively feeding back the divided voltage of the second reference voltage to the linear power circuit; and a comparing portion, comparing the second reference voltage with the monitoring target voltage or the divided voltage of the monitoring target voltage applied to the input terminal.

Voltage monitoring circuit

An electronic circuit is configured to output an output signal after elapse of a predetermined time from a received trigger signal, and includes an oscillator configured to output a pulse signal having a predetermined oscillation frequency; a counter circuit configured to count the pulse signal from the oscillator upon receiving the trigger signal and to output the output signal in response to a count value reaching a predetermined value; and a trimming circuit including a plurality of trimming elements which includes a cuttable conductive part and configured to output a selection signal corresponding to a trimming element having a cut conductive part. In the trimming circuit, the trimming element, which corresponds to the oscillation frequency of the pulse signal output from the oscillator among the plurality of trimming elements, is cut, and the counter circuit is configured to set the predetermined value according to the selection signal.

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Kyoto, Japan

Hiroyuki Makimoto