Protecting device

Abstract

Abstract PURPOSE: To protect the MOSFETs of the output stage by using enhancement type FETs for output elements, detecting the sum of the drain-source voltages and gate- source voltages of the FETs or the gate-source voltages in a power amplifier and cutting off inputs and outputs. CONSTITUTION: The protection circuit for a push-pull negative feedback power amplifier 12 is constituted by an enhancement type N channel MOSFET 1, likewise a P channel MOSFET 2, a load 3, resistances 8 thru 10, a PNP transistor 11. With such constitution, the sum of the drain-source voltages divided by the resistors 10 and 8 is detected and when this exceeds a fixed value the transistor 11 is conducted, in order to protect the output stage MOSFETs 1, 2 when a shorting or the like occurs in the load 3. Other circuits such as relay, SCR, transistor, etc. are driven by this current, by which the input terminals 16, 17 of the amplifier 12 are cut off. Thereby, the protecting device is made simple COPYRIGHT: (C)1979,JPO&Japio

Inventors

• 👤 Kazuhiro Tasaka

Bibliographic Details