Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific voltage responsive fault sensor
Patent
1979-02-14
1981-04-28
Larkins, William D.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific voltage responsive fault sensor
307304, 357 13, 357 35, 357 42, 357 43, 361 56, H01L 2704, H02H 904, H02H 720
Patent
active
042649412
ABSTRACT:
A protective circuit for integrated circuits having insulated gate field-effect transistors is disclosed which prevents high potentials resulting from manufacturing, installation, handling, testing or operation from damaging the gate oxide of the field-effect transistors and protective diodes associated with the input of the integrated circuit. The protective circuit includes a first vertical bipolar transistor which has its emitter-to-collector circuit connected in parallel with a first protective diode so that the anode of the diode is connected to the emitter and the input and the cathode of the diode is coupled to the collector and the drain power supply terminal of the field-effect transistors. The inherent distributed resistance of a doped region located within the substrate of the integrated circuit is coupled between the input and the base of the first bipolar transistor. A second lateral bipolar transistor, of an opposite conductivity type than the first bipolar transistor, has its emitter to collector circuit connected in parallel with a series connection of the inherent distributed resistance of the doped region and a second protective diode which is poled in an opposite orientation to the first diode with respect to the input. The cathode of the second diode is connected to the doped region's inherent resistance and the anode of the second diode is connected to the source power supply terminal. The inherent distributed resistance of the substrate of the integrated circuit is coupled between the base of the second transistor and the cathode of a low voltage reverse breakdown diode which conducts in the reverse biased direction during conduction of the second transistor. The emitter of the second bipolar transistor is connected to the input and the collector of the transistor is connected to the anode of the low voltage reverse breakdown diode and the source power supply terminal.
The application of a high potential to the integrated circuit which is of sufficient magnitude to rupture the gate oxide of the insulated gated field effect transistors causes conduction of the first or second bipolar transistors before irreversible damage of the protective diodes or the rupture of the gate oxide of the input field effect transistors of the integrated circuit can occur.
REFERENCES:
patent: 3739238 (1973-06-01), Hara
patent: 3787717 (1974-01-01), Fischer et al.
patent: 3865649 (1975-02-01), Beasom
patent: 4100561 (1978-07-01), Ollendorf
patent: 4131908 (1978-12-01), Daub et al.
Larkins William D.
National Semiconductor Corporation
Sheridan James A.
Woodward Gail W.
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