Abstract: An electronic device for use in an automobile includes first and second power transistors connected in series between two power supply terminals, a first detector producing a first detection signal when the voltage difference between the two power supply terminals is larger than a first predetermined value, and a second detector producing a second detection signal when the voltage difference between the two power supply terminals is larger than a second predetermined value which is larger than the first value, the first power transistor being driven into cut-off in response to the first detection signal and a control current to be applied to the second power transistor being bypassed to one of the power supply terminals to keep the second power transistor conductive.

Abstract: A demodulator for demodulating an amplitude modulated signal of a carrier signal. The demodulator provides a high output and is suitable for use in integrated circuitry. An input signal is connected to the base of one transistor of a pair of transistors forming an input differential amplifier. The input differential amplifier is stably biased by means of a constant current generator, diodes, input resistors and collector resistors. The two opposite phase output voltages from the differential amplifier are applied to the bases of a pair of transistors which have their collectors and emitters tied together. The output from the latter transistor pair is taken from the common emitter connection and it is applied directly to the base of an emitter follower transistor, the output from the latter constituting an output from the demodulator circuitry. The particular circuit arrangement provides significant elimination of the carrier frequency and provides filtering by parasitic capacitances of the transistors.

Abstract: A power circuit is comprised of a control transistor connected in series between one terminal of a power source and one terminal of a load, an error detecting amplifier circuit for detecting and amplifying changes of the load voltage, a drive transistor for driving the control transistor in response to the output current from the error detecting amplifier circuit, an input-output voltage difference detecting transistor which conducts when the difference between the input and the output voltages of the control transistor decreases to below a predetermined value, and a shunt transistor for shunting the current supplied to the drive transistor when it is activated by the output current of the input-output voltage difference detecting transistor. The power circuit operates as a constant voltage circuit when the input voltage is not lower than the predetermined value, while it operates as a ripple filter with a wide operable range when the input voltage decreases to below the predetermined value.