| 摘要 |
PURPOSE:To prevent power consumption performed wastefully by providing a bias power source to supply a bias voltage to a voltage-current converter, a selection means to select the bias voltage at a prescribed voltage, and a control means to control the selection means based on an operating mode. CONSTITUTION:A selection switch 8 is the selection means to switch the bias voltage to be supplied to the voltage-current converter 2 to either -VEE1 or -VEE2. A control circuit 9 supplies the bias voltage -VEE1 to the voltage- current converter 2 by switching the selection switch 8 to continuous line side in a Doppler mode. Meanwhile, in a B mode, the bias voltage -VEE2 is supplied to the voltage-current converter 2 by switching the selection switch 8 to broken line side. A ratio of power consumed between the emitter of the input transistor of the voltage-current converter 2 and the voltages -VEE1 and -VEE2 goes to around 1/(VEE1/VEE2)<2>. The ratio can be further increased by considering the voltage between the base and the emitter of the transistor. Therefore, it is possible to remarkably reduce the power consumption by switching the bias voltage based on the operating mode. |
