Abstract: An overcurrent detecting circuit and reference voltage circuit may reduce the current consumed by an electronic circuit. The circuit may includes a reference load through which a reference current flows, generating a reference voltage. A differential amplifier section is included to amplify the difference in the potentials of two inputs. At least part of a bias current supplied by a constant current source to the differential amplifier section flows to the reference load. A detection voltage, corresponding to a current subject to overcurrent detection, is inputted to one of the two inputs of the differential amplifier section.

Abstract: A series regulator for supplying a stable output voltage to a load has a differential amplifier circuit and an output stage. The output stage has an output control transistor that supplies the output voltage in accordance with a control signal, and a voltage divider circuit that divides the output voltage and outputs the divided voltage. The differential input stage includes a differential pair (source-coupled pair) of two NMOS transistors, an NMOS transistor, and a current mirror circuit formed by PMOS transistors. The differential input stage detects a differential voltage between a reference voltage and the divided voltage output from the voltage divider circuit. The differential amplifier circuit also has an amplification stage including a PMOS transistor that has a resistor connected between its gate and drain and that has its drain connected to a node, and an NMOS transistor that supplies a current proportional to a constant current to the PMOS transistor.

Abstract: A DC to DC converter includes a current detecting circuit having a level shift circuit, which includes a resistor and a current source. A first low-pass filter is led out from a node via a signal line and includes a resistor and a capacitor. A first switch is provided after the level shift circuit, a second switch is provided after the low-pass filter, a second low-pass filter, which includes a resistor and a capacitor, an operational amplifier, a third switch is provided between an output terminal and an inverted input terminal of the operational amplifier, and a capacitor is provided between the inverted input terminal of the operational amplifier and GND. An output current is detected with high accuracy without lowering the efficiency by detection resistance.

Abstract: An air-fuel ratio control system for a gas-fueled engine which is capable of achieving the combustion in a target air-fuel ratio to surely purify an exhaust gas through an exhaust purification catalyst. In the air-fuel ratio control system, a three-way catalytic converter is placed in an exhaust pipe of the engine and an O2 sensor is located on the upstream side of the three-way catalytic converter. The O2 sensor comprises an element, and an atmosphere side electrode is formed on an inner surface of the element while an exhaust gas side electrode is formed on an outer surface thereof. The exhaust gas side electrode is coated with a catalyst layer which can remove hydrogen through a catalytic reaction. A control unit of the control system controls a fuel supply quantity by a gas injector using a feedback correction coefficient on the basis of the output of the O2 sensor, thereby reducing the deviation between an air-fuel ratio measured by the O2 sensor and a target air-fuel ratio.