JPS5951750B

PURPOSE:To minimize voltage drop of a diode and thus to prevent electron injection by controlling a transistor provided in parallel with a diode to output a negative potential in a substrate biasing circuit in MOS IC. CONSTITUTION:Transistors Q1, Q2 are driven by an oscillator 1 to output to the first node N2 by way of a capacitor C1. Then, transistors Q6, Q7 are driven on external signals VA, VB to supply output opposite phase to the output to the first node N2 to the second node N3 by way of a capacitor C2. There are provided the first transistor Q3 conducting when the first node N2 is at high potential and clamping to a grounding potential and a diode D1 conducting when the first node N2 is at low potential and making the output bias negative in potential, and the second transistor Q4 controlled by potential of the second node N3 is connected to the diode D1 in parallel.