PURPOSE: To protect input protective diodes from breakdown and prevent latch-up due to excessive input current by connecting resistive components between the diodes and an input pin to give the input current paths a resistive characteristic instead of a diode characteristic if excessive current appears at the input.

CONSTITUTION: Input protective diodes 3 and 4 are connected to an input pin 1 through resistors 10 and 11, respectively. If a positive input voltage at the input pin exceeds a source voltage, the diode 3 turns on, but the input current is limited by the resistor 10. If a negative input voltage is applied to the input pin, on the other hand, the diode 4 turns on, but the input current is limited by the resistor 11. Since the input current is limited at an excessive input voltage in this manner, the diodes are protected from breakdown, and latch-up due to excessive input current is also prevented.