Integrated circuit

Claim 2

An integrated circuit comprising an input circuit, an input terminal, means for connecting said input terminal to said input circuit, a bipolar-transistor having a collector, a base and an emitter, a reference voltage terminal, means for connecting said collector of said transistor to said input terminal, and means'for connecting said emitter of said transistor to said reference voltage terminal, wherein an excessive voltage applied to said input terminal is discharged to said reference voltage terminal through said transistor.

Claim 3

The integrated circuit according to claim 1, in which said base of said transistor is held at a relatively high impedance state.

Claim 4

The integrated circuit according to claim 1, further comprising a resistor having one end connected to said base of said transistor and the other end connected to said collector.

Claim 5

A semiconductor integrated circuit comprising a semiconductor substrate, an input terminal, a first voltage terminal receiving a first power voltage, an input circuit fabricated on said semiconductor substrate, said input circuit performing a logic operation in response to an input signal of a given voltage range applied thereto, said input circuit including at least one functional transistor operable with said first power voltage and a second power voltage, a protective element formed on said substrate, said protective element including a first semiconductor region of a first conductivity type, a second semiconductor region forming a first PN junction with said first semiconductor region, and a third semiconductor region forming a second PN junction with said second semiconductor region, first means connecting said input terminal to said input circuit, second means for connecting said first semiconductor region to said input terminal, and third means for connecting said third semiconductor region to said first voltage terminal, said second semiconductor region being kept at a relatively high impedance, whereby an excessive voltage outside said given voltage range applied to said input terminal is discharged to said first voltage terminal through said first to third semiconductor region.

Claim 6

A semiconductor integrated circuit comprising a semiconductor substrate, an input terminal, a first voltage terminal receiving a first power voltage, an input circuit fabricated on said semiconductor substrate, said input circuit performing a logic operation in response to an input signal of a given voltage range applied thereto, said input circuit including at least one functional transistor operable with said first power voltage and a second power voltage, a protective element formed on said substrate, said protective element including a first semiconductor region of a first conductivity type, a second semiconductor region forming a first PN junction with said first semiconductor region, and a third semiconductor region forming a second PN junction with said second semiconductor region, first means connecting said input terminal to said input circuit, second means for connecting said first semiconductor region to said input terminal, and third means for connecting said third semiconductor region to said first voltage terminal, said second semiconductor region being kept at a relatively high impedance, whereby an excessive voltage outside said given voltage range applied to said input terminal is discharged to said first voltage terminal through said first to third semiconductor region.

Claim 7

The circuit according to claim 4, in which said functional transistor is a bipolar transistor and an emitter of said bipolar transistor is coupled to said first voltage terminal.

Claim 8

The circuit according to claim 4, in which said functional transistor is a field effect transistor and a source of said field effect transistor is coupled to said first voltage terminal.

Claim 9

The circuit according to claim 4, in which said second semiconductor region is kept in open state.

Claim 10

The circuit according to claim 4, in which said second semiconductor region is connected to said first voltage terminal through a resistor.

Claim 11

In the combination of: a protected electronic device arranged to receive and operate on input signals of a given voltage range supplied thereto between two input terminals thereof and which is susceptible of damage of the voltage of an input signal supplied thereto exceeds a predetermined value, which is beyond said given range, and a voltage sensitive protecting means connected between said two input terminals and arranged to present (a) a relatively high impedance between said two input terminals so as not to affect said input signal and thereby not to affect the operation of said protected device when the voltage of said input signal does not exceed said given range, and (b) a relatively low impedance between said two input terminals so as to reduce the voltage of said input signal and thereby protect said protected device when the voltage of said input signal exceeds said given range, the improvement wherein said voltage sensitive protecting means comprises a bipolar transistor having a collector-emitter path connected between said two input terminals and a base kept at relatively high impedance state so as not to conduct if the input signal does not exceed said predetermined value.

Claim 12

In the combination of: a protected electronic device arranged to receive and operate on input signals of a given voltage range supplied thereto between two input terminals thereof and which is susceptible of damage of the voltage of an input signal supplied thereto exceeds a predetermined value, which is beyond said given range, and a voltage sensitive protecting means connected between said two input terminals and arranged to present (a) a relatively high impedance between said two input terminals so as not to affect said input signal and thereby not to affect the operation of said protected device when the voltage of said input signal does not exceed said given range, and (b) a relatively low impedance between said two input terminals so as to reduce the voltage of said input signal and thereby protect said protected device when the voltage of said input signal exceeds said given range, the improvement wherein said voltage sensitive protecting means comprises a bipolar transistor having a collector-emitter path connected between said two input terminals and a base kept at relatively high impedance state so as not to conduct if the input signal does not exceed said predetermined value.