| 摘要 |
PURPOSE:To enable the measuring of AC characteristic of a sample, by maintaining the terminal voltage for DC component of the sample regardless of changes in the voltage drop and flowing current of the sample. CONSTITUTION:The output difference voltage of a DC power source 11 and an amplifier 18 is amplified 13 and a reference potential runs by way of a primary winding T1, AC signal source 1, a diode D3, a range resistor 4, an operational amplifier 5, a secondary winding T2 and the like. At this point as the input impedance of the amplifier 18 is large, current fails to flow through resistors 6 and 19 and dropped DC voltage across the D3 is inputted into the input terminal of the amplifier 18. As the amplification factor of the amplifier 18 is 1, the terminal voltage for DC component of the D3 is inputted into an amplifier 14. The differential voltage between this voltage and a power source 11 is amplified 13 and a loop is formed with the winding T1, the signal source 1, the D3, the resistor 6 and 19, the amplifier 18 and the like. This loop becomes stable, as the output voltages of the power source 11 and the amplifier 18 come to equal and the terminal voltage for DC component of the D3 will be equal to the voltage of the power source 11. So, the voltage of the power source 11 is shifted to a specified value and the DC terminal voltage of the D3, namely, the DC bias voltage is set at a specified value and the AC characteristic of the D3 is measured.
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