PURPOSE:To obtain a sin2 waveform with high quality by using an integration circuit so as to shape a trapezoidal wave thereby obtaining a trapezoidal wave whose straight line part of slope is symmetrical. CONSTITUTION:With an input signal (vin) changed from zero to 5V at a point of time t1, a diode 5 is turned off, the integration circuit comprising a resistor 2, an operational amplifier 3 and a capacitor 4 is driven and an intermediate signal vt falls down until a diode 6 is turned on. With the diode 6 turned on, the intermediate signal vt is constant (=2.5V-VD). With a rectangular wave Vin changed from 5V to zero at a time t2, a diode 6 is turned off and the intermediate signal vt rises linearly until the diode 5 is turned on. thus, a trapezoidal wave whose amplitude is 2VD around the bias potential (2.5V) is obtained as the intermediate voltage vt. Then the intermediate signal vt is fed to a differential circuit combined with transistors 9, 10 and in selecting the ratio of input resistors 8, 11 properly, an output signal vout sujected to sin2 shaping is extracted at an output terminal 17.
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