PURPOSE: To reduce the space by utilizing the constant current characteristic of a transistor (TR) and applying level shift between a low voltage part and a high voltage part to allow the use of a coupling capacitor with low dielectric strength.

CONSTITUTION: A signal inputted from the low voltage part circuit 1 to an input terminal 4 is inputted to the base of a TR10, the DC level is decreased by a VBE (base-emitter voltage of the TR, nearly 0.7V), the voltage shift is caused to the emitter to form a voltage across an emitter resistor 11. In selecting an hFE of the TR10 sufficiently large and a resistance value of resistors 11, 12 identically, the voltage across the resistors 11 and 12 is identical to each other. In selecting an hFE of a TR13 sufficiently large and the resistance value of resistors 14, 15 identically, a signal inputted from the input terminal 4 goes to a signal component across the resistor 15 as it is, and the level is shifted by the potential difference between the potential of terminals 9 and 7 in terms of the potential. Thus, the dielectric strength of a capacitor 16 coupled to the high voltage part circuit 2 is decreased.