PURPOSE: To enable the action of a low temperature test at normal temperature by a method wherein a current source which can reduce an injector current only in test modes is provided in an I2L circuit.

CONSTITUTION: The I2L circuit is so constructed as to supply a current to the bases of a multi-collector transistors 10 and 12 with a substrate as the emitters from a current supply circuit 21 via transistors 9 and 11 of reverse conductivity types and to impress an input signal via terminals 4 and 6. Here, the circuit 21 constitutes a variable current circuit which can take binary current values large and small, having a terminal 22 besides a power source terminal 20. The terminal 22 is put at a low level in normal operation and supplies a normal injector current. On the other hand, the injector current decreases in testing by putting the terminal 22 at a high level, thus becoming under the same condition of current as in the case of low temperature.