Abstract: A circuit for use with an ignition system to enable detection of an overvoltage condition in the primary winding of an ignition coil caused by opening of a power switch connected to the primary winding. The circuit senses the overvoltage condition by comparing the voltage on the primary winding to a first threshold voltage and produces a signal at an output terminal indicative of the presence of the overvoltage condition. The output terminal is maintained at a high logic level upon detection of an overvoltage condition and throughout the time duration of the overvoltage condition, and drops to a low logic level when the voltage on the primary winding falls to a second threshold voltage, which is lower than the first threshold voltage. Comparison circuitry is provided for sensing the overvoltage condition by reference to fixed voltage values. Logic circuitry responds to the comparison circuitry to produce the appropriate logic levels at the output terminal.

Abstract: A circuit to limit the maximum current passed from a power transistor (T'p) to a load (ZL) which is connected to an output terminal of the transistor. The circuit includes an error amplifier (1'), a driver circuit (P') for the transistor (T'p), and a current detector for detecting the current (IL) flowing through the load (ZL). The current detector is provided with at least first and second terminals, includes a circuit block (2) having an input terminal connected to the control terminal of (T'p) and an output terminal connected to the current generator internal to the amplifier (1'), one input (B') of the amplifier (1') being connected to the first terminal of (Rs) and the other input (A') connected to the second terminal of (Rs). The introduction of the circuit block lowers the open-loop system gain making it stable and producing a smooth reduction of any rise in the load current (IL).

Abstract: A bandgap voltage reference circuit employs a Vbe voltage multiplier network in a feedback line of an output amplifier of the bandgap reference circuit, thus permitting to independently fix the output voltage that is produced and the temperature coefficient thereof. A voltage reference having a linear negative temperature coefficient in an extended temperature variation range may be obtained, starting from a bandgap reference voltage with a positive temperature coefficient.