초록 ▼

An external FET (12) has protection provided thereto for excessive voltages between the gate and drain and between the gate and source. A drain-to-gate clamp is provided with a plurality of series connected zener diodes (34), (36) and (38) which are connected in series with a Schottky diode (42). Th

An external FET (12) has protection provided thereto for excessive voltages between the gate and drain and between the gate and source. A drain-to-gate clamp is provided with a plurality of series connected zener diodes (34), (36) and (38) which are connected in series with a Schottky diode (42). The current therethrough is sensed with a resistor (56) which turns on a bypass transistor (58) to shunt current around the zener diodes when an excess voltage causes them to break down. This will turn on the FET (12). The gate-to-source clamp is configured with two zener diodes (74) and (76) which are reversed biased. A series current sense resistor (82) senses the current through the diodes and turns on a transistor (84) when the current exceeds a predetermined level. This will effectively shunt current around the zener diodes (74) and (76).

대표청구항 ▼

[ What is claimed is:] [1.] A clamp circuit for being disposed between the gate and one of the source/drain terminals of an external transistor for preventing a large voltage from being impressed across the gate oxide of the external transistor, comprising:a threshold device having a high voltage si

[ What is claimed is:] [1.] A clamp circuit for being disposed between the gate and one of the source/drain terminals of an external transistor for preventing a large voltage from being impressed across the gate oxide of the external transistor, comprising:a threshold device having a high voltage side and a low voltage side for conducting current between the gate and the one of the source/drain terminals of the external transistor when the voltage thereacross exceeds a first threshold voltage to prevent the voltage thereacross from rising substantially above the first threshold voltage; anda current bypass circuit for bypassing a portion of the current from the high voltage side of the threshold device to the low voltage side thereof when the current through said threshold device rises above a predetermined bypass current threshold.