DELAY CIRCUIT AND ULTRASONIC DIAGNOSING DEVICE USING THIS CIRCUIT

摘要

PURPOSE:To continuously variably set the delay time with an electric signal and to prevent the occurrence of noise even at the time of changing the delay time by providing a variable delay line consisting of inductors and varactor diodes. CONSTITUTION:The input signal of a delay circuit is applied to an input signal terminal IN. A resistance r1 on the collector side gives the collector potential of a transistor TR Q1, and the TR Q1 functions as a constant current signal source when its resistance value is set to a sufficiently high value. A variable delay line 100 constituted by cascading many inductors L and varactor diodes C' is driven by the constant current signal source. The electrostatic capacity is changed in accordance with the bias voltage of diodes C' to control the delay time of the variable delay line 100. The resistance value of a variable resistance circuit 110 is controlled by the voltage of a control signal terminal B so that the characteristic impedance value is equalized which is changed in accordance with the change of the delay time of the variable delay line 100 due to the control signal voltage of a control signal terminal A. Thus, the delay time is continuously variably set.