PURPOSE: To reduce the dispersion of oscillation frequency and to make stable the circuit for temperature change, by using two differential amplifiers and determining the reference level with resistance ratio only.

CONSTITUTION: Transistors Q1,Q2 and Q3,Q4 respectively constitute two differential amplifiers, the base bias of Q1 is given by the voltage division circuit of resistors R1 and R2 at Q11 OFF, and the bias for Q4 is given by the voltage division circuit of R3 and R4 at Q10 OFF. Q11,Q10 controlling the base bias of Q1,Q4 are controlled with the output of the sum of two differential amplifiers. Further, Q10,Q11 are controlled so that they are operated at non-saturation region with the control of Q6∼ Q9 and Q13 together with Q14 constituting the discharge path of the oscillation capacitor CH, so as not to give effect on the storage time for the switching operation of two differential amplifiers.