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如图所示的电路是用555时基集成电路构成的方波脉冲振荡器。定时电容器C_1的充电和放电是经过VD1—VD4二极管桥路及由晶体VT3、VT4组成的二个电流源实现的。电流源VT3、VT4的工作由晶体管VT2控制,调电位器R_2可以线性地改变输出方波的频率。在电路所示元件参数情况下,可以获德20倍频程的频率变化。电位器R_2在中间位置时,振荡频率约1kHz。
The circuit shown in the figure is a square wave pulse oscillator composed of 555 time base integrated circuits. The timing capacitor C_1 is charged and discharged through two VD1-VD4 diode bridges and two current sources consisting of transistors VT3 and VT4. Current source VT3, VT4 work by the transistor VT2 control, adjustable potentiometer R_2 can be linearly change the output square wave frequency. In the circuit shown in the case of component parameters, Germany can be 20 times the frequency of change. Potentiometer R_2 in the middle position, the oscillation frequency of about 1kHz.