Abstract: In a load-driving apparatus with a FET between a battery and a load, an overcurrent detection circuit has a function generation circuit with a voltage divider circuit and a comparator. The voltage divider circuit has a pair of resistors connected to a drain of the FET, and a Zener diode connected to a connection point in parallel to the second resistor. The comparator compares a reference voltage at the connection point with a variable voltage of the FET, and outputs an overcurrent detection signal when the variable voltage becomes lower than the reference voltage. When no overcurrent exists and the battery voltage is not decreasing, the connection point is kept at a breakdown voltage of the Zener diode, and the difference with respect to the source voltage of the FET becomes particularly large. The comparator therefore does not erroneously output an overcurrent detection signal even when noise enters the system.

Abstract: In a load-driving apparatus with a FET between a battery and a load, an overcurrent detection circuit has a function generation circuit with a voltage divider circuit and a comparator. The voltage divider circuit has a pair of resistors connected to a drain of the FET, and a Zener diode connected to a connection point in parallel to the second resistor. The comparator compares a reference voltage at the connection point with a variable voltage of the FET, and outputs an overcurrent detection signal when the variable voltage becomes lower than the reference voltage. When no overcurrent exists and the battery voltage is not decreasing, the connection point is kept at a breakdown voltage of the Zener diode, and the difference with respect to the source voltage of the FET becomes particularly large. The comparator therefore does not erroneously output an overcurrent detection signal even when noise enters the system.

Abstract: Operational amplifier circuitry is provided which comprises an operational amplifier having a first input port and a second input port, and a compensating circuit for making a voltage difference between the first and the second input ports of the operational amplifier substantially equal to the offset voltage of the amplifier, compensating the bias currents of the operational amplifier. The compensating circuit may include a series of a first resistor and a second resistor connected between the first and the second input ports of the amplifier. The node connecting the first and the second resistors is coupled to a predetermined voltage, the resistances of the first and the second resistors being selected so that a voltage difference between the first and the second input ports of the amplifier is substantially equal to the offset voltage of the operational amplifier.

Abstract: For a gas turbine engine provided with a fuel feed control system that includes an engine speed sensor and provides a fuel feed rate control signal based on the deviation of the sensed engine speed from an intended speed, the invention provides a system for detecting the presence of an abnormality possibly leading to an overrun of the engine shortly after starting of the engine. This system comprises a timer circuit which produces a signal such as logic "1" signal after the lapse of a preset period of time from starting of the engine, a comparison circuit which produces a signal such as logic "1" signal if the amplitude of the actual engine speed signal is below a normally expected level after the lapse of the preset period of time, and a logical operation circuit which provides a warning signal only when, for example, the outputs of the timer and comparison circuits are both "1" signals.