Abstract: An electronic accessory, powered by a battery having a first terminal and a second terminal includes a voltage comparator capable of comparing the battery voltage to at least one reference voltage and that generates a voltage comparator signal having a value that is a function of the battery voltage relative to the reference voltage. A gain control circuit couples an input signal to a first signal path when the voltage comparator signal is above a first value and to a second signal path when the voltage comparator signal is below a second value. The first signal path includes a first component that causes an amplifier to have a first gain. The second signal path includes a second component that causes the amplifier to have a second gain.

Abstract: A two-stage power supply start up circuit is provided for pulse width modulator controllers that operate at a low steady state voltage. The invention provides for high-energy storage in low-capacitance start up capacitors by cascading switched start up stages, thereby allowing for the utilization of smaller, less expensive components. The invention utilizes a three-phase start up process with positive feedback ensuring both reliable start-up and steady state operation. The three phases are as "first phase start-up", which provides power to the control circuit, "second phase start-up", where the control chip starts switching, and "steady state", where the power supply runs in its normal mode.

Abstract: A laser diode protection circuit which monitors the r.f. modulation level of the input modulating signal to the laser diode and disconnects the laser diode from the r.f. modulating signal when it exceeds an acceptable level. The circuit further monitors the output of the d.c. power supply which provides the d.c. bias current to the laser diode. The circuit disconnects the laser diode from the r.f. modulating signal when the output of the power supply falls below an acceptable level.