Abstract: A protective apparatus for a power transistor which detects an abnormal temperature of a power transistor and cuts a load to the power transistor to prevent possible breakdown of the power transistor. The protective apparatus comprises detecting means which detects a junction temperature of the power transistor on the real time basis from a base-emitter voltage of the power transistor. When the junction temperature of the power transistor is excessively high, a protective circuit produces an output signal, and a muting circuit applies muting to an input signal to or a current flow through the power transistor.

Abstract: A reverberation circuit comprises an amplifier, attenuation circuit, a feedback component, and a delay circuit. The amplifier, delay circuit, and feedback component form a feedback loop. The amplifier amplifies an input signal supplied to an input terminal and outputs an amplified signal to the delay circuit. The output of the delay circuit is fed through a feedback component back to the amplifier. The feedback component controllably varies the feedback amount of the delayed signal to the amplifier in accordance with the desired depth of reverberation. An attenuation circuit is placed in the feedback loop, or before or after the feedback loop. The attenuation circuit selectively attenuates the level of specific frequency component of a signal passing therethrough whose frequency may be different depending on the depth of reverberation or feedback amount.