| 摘要 |
PURPOSE:To attain high performance by means of one power supply system by constituting the titled amplifier by the 1st operational amplifier integrating an input analog voltage, the 2nd operational amplifier as a comparator and a single power supply actuating both the operational amplifiers. CONSTITUTION:A pulse width modulation circuit 1 consists of an integration device receiving an analog input voltage Vin and a comparator comparing an output of the integration device with a reference potential, inverting the polarity of the output voltage depending on the quantity of comparison result and outputting an on/off pulse. The integration device consists of the 1st operational amplifier Q1, an input resistor Rin and a capacitor C, the comparator consists of the 2nd operational amplifier Q2, Zener diodes ZD1-ZD3, and a current limit resistor R8, and the power supply is a single power supply E. A current IC1 flows to the capacitor C when an output V02 of the comparator is saturated positively (VP), and a current IC2 flows to the capacitor C at negative saturation VN. The period at +VP is TON and the period at VN is TOFF and the duty ratio of the pulse width modulation circuit 1 is proportional to the input voltage. Thus, the stable isolation amplifier is obtained.
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