Patent EP0257774A1 successfully refreshed from Google Patents.
EP0257774A1
Expired / Lapsed
EP
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Protection circuit for large-scale integrated circuit
Assignee: Fujitsu Ltd
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Filing: 1987-07-17
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Granted: —
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Expires: 2007-07-17
Abstract
Abstract A protection circuit for a large-scale integrated circuit includes a metal insulator semiconductor transistor (Q1) to be protected, a resistor (R1) connected between an external terminal (I) and the gate of the transistor (Q1) to be protected, a protecting transistor (Q3) having a base which is a well region of a substrate of the large-scale integrated circuit, and an auxiliary transistor (Q4) connected between the base of the protecting transistor (Q3) and a voltage source (V SS ). The auxiliary transistor (Q4) causes the base of the protecting transistor (Q3) to become a floating state when the large-scale integrated circuit is not energized by a power source (V CC ) and causes the base of the protecting transistor (Q3) to become conductive with the voltage source (V SS ) when the large-scale integrated circuit is energized by the power source (V CC ).
Inventors
- 👤 Shigenobu Taira
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 13:08
CPC Classifications
H; H10; H10D; H10D89/00; H10D89/60; H10D89/601; H10D84/00; H10D84/40; H10D84/401
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
198 words
A protection circuit for a large-scale integrated circuit comprising: a metal insulator semiconductor transistor (Q1) to be protected; a resistor (R1) connected between an external terminal (I) and the transistor (Q1) to be protected; a protecting transistor (Q3) having a first electrode connected with the junctinon of the gate of the transistor (Q1) to be protected and the resistor, and a second connected to a voltage source (V SS ); and, an auxiliary transistor (Q4) connected between a third electrode of the protecting transistor (Q3) and the voltage source (V SS ); characterised in that the first electrode of the protecting transistor (Q3) is a collector, the second electrode is an emitter and the third electrode is a base formed in a well region formed in the substrate of the large-scale integrated circuit; and in that the auxiliary transistor (Q4) causes the base of the protecting transistor (Q3) to have a floating state when the large-scale integrated circuit is not energized by a power source and causes the base of the protecting transistor (Q3) to become conductive with the voltage source (V SS ) when the large-scale integrated circuit is energized by the power source (V CC ).
Claim 2
Dependent Claim
198 words
A protection circuit for a large-scale integrated circuit comprising: a metal insulator semiconductor transistor (Q1) to be protected; a resistor (R1) connected between an external terminal (I) and the transistor (Q1) to be protected; a protecting transistor (Q3) having a first electrode connected with the junctinon of the gate of the transistor (Q1) to be protected and the resistor, and a second connected to a voltage source (V SS ); and, an auxiliary transistor (Q4) connected between a third electrode of the protecting transistor (Q3) and the voltage source (V SS ); characterised in that the first electrode of the protecting transistor (Q3) is a collector, the second electrode is an emitter and the third electrode is a base formed in a well region formed in the substrate of the large-scale integrated circuit; and in that the auxiliary transistor (Q4) causes the base of the protecting transistor (Q3) to have a floating state when the large-scale integrated circuit is not energized by a power source and causes the base of the protecting transistor (Q3) to become conductive with the voltage source (V SS ) when the large-scale integrated circuit is energized by the power source (V CC ).
Claim 3
Dependent Claim
33 words
A protection circuit according to claim 1, wherein the transistor to be protected (Q1) and the auxiliary transistor (Q4) are metal insulator semiconductor transistors, and the protecting transistor is a lateral bipolar transistor.
Claim 4
Dependent Claim
29 words
A protection circuit according to claim 1 or 2, wherein the resistor (R1) is constituted by a diffusion resistor region formed in the substrate of the large-scale integrated circuit.
Claim 5
Dependent Claim
38 words
A protection circuit according to any one of the preceding claims, wherein the transistor to be protected is constructed in the form of complementary metal insulator semiconductor transistors (Q1,Q2; Q1ʹ,Q2ʹ), the gates of which are connected in common.
Claim 6
Dependent Claim
34 words
A protection circuit according to any one of the preceding claims, wherein the external terminal (I) to which the resistor (R1) is conected is an input terminal pad (A9) of the large-scale integrated circuit.
Claim 7
Dependent Claim
32 words
A protection circuit according to any one of claims 1 to 4, wherein the external terminal (I) to which the resistor is connected is an output terminal of the large-scale integrated circuit.
References Cited (Backward Citations)
US3746946A
Cited
EP0055552A2
Cited
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