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常用的HC4046压控振荡器VCO的输出频率变化范围约为十倍,同时,当输入电压范围为1至4.75V时此器件显示出良好的线性。本电路使其频率变化范围加宽到10~3倍。这里由运放LM358和晶体管Trl组成一个压控电流陷(currentsink),来取代原接在(11)脚至地之间确定频率值的单个电阻。此电流陷克服了集成电流源通常对定时电容充、放电的很大限制。一个固定电平2.5V加到了VCO的输入端引脚⑨
The typical HC4046 voltage-controlled oscillator VCO output frequency range of about ten times, at the same time, when the input voltage range of 1 to 4.75V when the device shows good linearity. The circuit to widen the range of its frequency to 10 to 3 times. Here the op amp LM358 and transistor Trl form a voltage-controlled current sink (currentsink), to replace the original resistance (11) to determine the frequency of a single resistor between the ground. This current sink overcame the integrated current source is usually charged on the timing capacitor, a very large discharge limit. A fixed level of 2.5V is added to the VCO input pin ⑨