PURPOSE: To obtain a voltage controlled oscillator with high temperature stability without components having less temperature coefficient by providing a temperature compensating circuit giving a temperature compensating characteristic to an oscillated amplitude deciding an oscillated output frequency of the voltage controlled oscillator.

CONSTITUTION: An area ratio of emitters of transistors (TR) Q3, Q4 is selected nearly as Q3:Q3=10:1, and a voltage ΔFBE produced across a resistor R3 has a relation of ΔVBE=VTln(10 I 2/ I 1) (II) is obtained from equation of ΔVBE= (VBE)Q4-(VBE)Q3 ( I ) and Q3:Q4=10:1, where Vt is a thermoelectromotive force, 300K at room temperature. Relation of I 1= I 2=VBE/R3 (III) is obtained by a current mirror circuit comprising TRs Q7∼Q9. Moreover, a voltage VR4 produced across a resistor R4 is expressed as equation (IV). Relation of equation (V) is established, where VRR is a band gap reference voltage and a current I G flowing to a TRQ14 is given by equation (VI). That is a positive on negative optional temperature coefficient is given to the reference voltage VR by selecting properly the ratio of the resistors R4 and R3.