Vehicle radio or cassette player booster amplifier - has short circuit load protection which draws minimal or no signal current

摘要

The booster amplifier is for car radios and cassette players. The amplifier does not require separate supply switching from the radio etc. due to very low power consumption in the absence of an input signal. The circuitry is protected against short circuit overloads at its output terminals, the amplifier coming back into operation immediately the overload is removed. The input signal is fed initially both to a balanced pre-amplifier (11) and to a switching circuit. The switching circuit consists of an amplifier stage (35) followed by a diode-capacitor detector (36). The detector output together with that from the input to the amplifier output stage is fed to an AND gate (37) isolating the pre-amplifier in the absence of an input signal. Protection against short circuit loads is by a resistor (34) in the power line to the output stages.