Patent ID: 7928973

Claim:
A power supply circuit, comprising: a temperature gradient variable circuit that produces a gradient voltage whose voltage level varies with a temperature gradient commensurate with an ambient temperature; and a temperature gradient setting circuit that produces a first drive voltage of a load by adjusting the temperature gradient and/or the voltage level of the gradient voltage, wherein the temperature gradient variable circuit includes: a diode having an anode from which a reference gradient voltage is extracted, the anode being connected to an internal voltage application terminal via a first resistor, a first amplifier that produces a first gradient voltage by amplifying the reference gradient voltage by a first gain, a second amplifier that produces a second gradient voltage by amplifying the reference gradient voltage by a second gain that is greater than the first gain, a first DC voltage source that produces a first reference voltage, a third amplifier that outputs a difference between the second gradient voltage and the first reference voltage as a third gradient voltage, and a selector that selects, as the gradient voltage, one of the first gradient voltage and the third gradient voltage, depending on which has a higher voltage.