Abstract: The invention relates to a level shifter coupled to a circuit of a predetermined value, includes a differential amplifier with a first input coupled to the reference voltage and a second input receiving an intermediate voltage; a low impedance source providing the reference voltage; and a first operational amplifier providing the intermediate voltage from an input voltage. The output of the low impedance source is directly connected to the first input of the differential amplifier and the gain of the first operational amplifier is set to obtain a desired ratio between the reference voltage and the intermediate voltage.

Abstract: An end-of-charge detection technique for a battery charger is described. The technique involves the detection of a voltage drop at the end of charging and eliminates the effect of noise spikes.

Abstract: An end-of-charge detection technique for a battery charger is described. The technique involves the detection of a voltage drop at the end of charging and eliminates the effect of noise spikes.

Abstract: A transmit amplifier for a telephone set without its own power supply has an LED with an anode connected to a first positive terminal of the telephone line and a circuit that determines the ratio between the line current and the line voltage. The LED is supplied with a constant current and this current is derived when the voltage across the terminals of the line becomes lower than a predetermined value.

Abstract: The current invention provides circuitry for use in an integrated circuit controlled voltage doubler/bridge circuit such that during any period wherein a lack of AC supply voltage is detected by the circuitry and following a period of AC input voltage within a lower defined range of values, repeated triac firing pulses are provided such that the AC supply will be rectified and doubled as soon as such a supply returns, whether the supply returns with the same or opposite polarity to that which it had, just before being interrupted.

Abstract: The present invention relates to a current sense device for a load arranged in a diagonal of a H-bridge comprising MOS transistors (M1, M2, M3, M4) and operating in class AB, characterized in that it includes sensor, independent from the H-bridge, for measuring the current flowing in the load. A current-voltage converter converts the current measured by said sensor into a voltage proportional to said current. The voltage is applied to a sense amplifier that determines the transconductance gain of a control amplifier of the transistors of the H-bridge.

Abstract: A technique for detecting power demand to provide efficient power sharing. The technique is particularly but not exclusively concerned with providing a power sharing detector for use in a portable computer which requires battery charging to be done concurrently with computer usage, and preferably provides three different rates of charging. A power sharing detector is provided for use with this technique. The power sharing detector is used in a circuit which has a power supply which supplies power both to an auxiliary device and a battery charger. The detector has a voltage detection circuit which is connected to receive a voltage representative of the power supplied to the auxiliary device and to determine therefrom a state of the auxiliary device.

Abstract: A source/sink current generating circuit is arranged to generate source and sink currents which are matched and insensitive to fan out. This is achieved by using a biasing transistor (Q13) between first and second current mirrors which generate respectively the source and sink currents.

Abstract: A parallel phone detection circuit is described, the function of which is to enable a phone call to be transferred from a first telephone set to a second telephone set. The detection circuit maintains the first telephone set connected to the telephone line until the handset of the second telephone set has been taken off-hook, and then disconnects the first telephone set. The circuit operates by detecting the line current from the telephone line and produces the reference value for comparison purposes related to that line current.

Abstract: An audio amplifier comprises a first current mirror having an input coupled to an output of a cascade differential pair and an output coupled to an output of a first constant current source. A second constant current source (Q16, Q18, CC10) supplies the voltage reference (Q15) of the first constant current source. Hitherto a resistor has been used instead of the second constant current source to reduce noise. However, using a resistor results in the amplifier having a relatively low power supply rejection ratio, thereby degrading the performance of the amplifier. Accordingly the present invention uses a second constant current source to improve the power supply rejection ratio without degrading the noise performance.