Patent ID: 8049572

Claim:
An oven-controlled crystal oscillator, comprising: a crystal unit in which a crystal blank is hermetically encapsulated and which includes a pair of connection terminals electrically connected to the crystal blank; an oscillating circuit element forming an oscillation circuit together with the crystal unit; a temperature control circuit maintaining operating temperature of the crystal unit constant; and a circuit board on which the crystal unit is surface-mounted, wherein the temperature control circuit includes at least a heating resistor, a power transistor supplying power to the heating resistor, and a temperature sensitive resistor detecting temperature of the crystal unit, wherein the heating resistor is formed, as a film resistor, on a surface of the circuit board in an area of the circuit board in which the crystal unit is located, wherein the temperature sensitive resistor is formed on the surface of the circuit board as a film resistor, wherein the crystal unit further includes: a pair of dummy terminals; a container body with a recess; and a metal cover joined to the container body, wherein the pair of the connection terminals and the pair of the dummy terminals constitute four mounting terminals which are used for surface-mounting the crystal oscillator on the circuit board and provided on an outer bottom surface of the container body, wherein four circuit terminals corresponding to the four mounting terminals, respectively, are formed on the surface of the circuit board, and wherein the heating resistor is formed in a cross-like planar shape in the area of the circuit board in which the crystal unit is located so that the heating resistor is separated from the circuit terminals, and the heating resistor faces to the outer bottom surface of the container body.