Function generator

摘要

In order to realize highly accurate temperature compensation of a crystal oscillation frequency, a current in proportion to the cube of a difference between an ambient temperature Ta and a reference temperature T0 is generated. For this purpose, provided are a first series circuit of two diodes; a second series circuit of three diodes; a third series circuit of two diodes; a fourth series circuit of three diodes; a current source for allowing a constant current to flow into the first series circuit; a current source for allowing a constant current to flow from the third series circuit; a current source for allowing a current in proportion to Ta-T0 to flow into the second series circuit when Ta>/=T0 and allowing a current in proportion to |Ta-T0| to flow from the fourth series circuit when Ta<T0; an NPN transistor and a PNP transistor whose collectors are connected with an output terminal; and two operational amplifiers for applying a voltage between the anode terminals of the first and second series circuits between the base and the emitter of the NPN transistor and for applying a voltage between the cathode terminals of the third and fourth series circuits between the base and the emitter of the PNP transistor, respectively.