Abstract: A signal amplifier circuit comprises a signal amplifier having an input for receiving an ac signal to be amplified and an amplifier biasing arrangement coupled between the signal input and a dc voltage line, the arrangement comprising a diode means and a bootstrapping amplifier connected across the diode means.

Abstract: A method of processing an analogue signal including the steps of converting the analogue signal into a width modulated pulse signal so timed by a clock pulse signal as to provide one width-modulated pulse for each clock pulse and generating, for each clock pulse, a resultant signal having a first level whenever either one of a clock pulse and a width-modulated pulse is present on its own and having a second level for all other relationships between the clock pulse signal and the width-modulated pulse signal.

Abstract: A portable radio transceiver has a gallium arsenide depletion mode n-channel field-effect transistor as the transmitter power supply amplifier which needs a negative supply applied to its gate to establish the correct working point. A positive power supply provides the power input to the gallium arsenide transistor and a high side switch in the form of a PMOS enhancement mode transistor is used to switch the transmitter on and off. The negative supply is also used to forward bias the gate of the PMOS transistor when conducting so as to reduce its forward conduction resistance thereby enabling a smaller transistor to be used which can be integrated with other low power devices used by the transceiver.