Abstract: The distortion component of an oscillation signal is reduced. An oscillation signal generating circuit generates, as oscillation signals, first generation oscillation signal and second generation oscillation signal which are related to each other as a differential signal. A differential amplifier performs differential amplification on the first generation oscillation signal and the second generation oscillation signal, respectively, and outputs first amplification oscillation signal and second amplification oscillation signal. A converter circuit converts the first amplification oscillation signal and the second amplification oscillation signal into an output current oscillation signal of such a form that sink current and source current are alternately switched. In order to convert voltages of the first amplification oscillation signal and the second amplification oscillation signal into currents, a variable current source delivers a converting drive current to drive the converter circuit.