| 摘要 |
PURPOSE:To control a threshold voltage of a FET to a desired value even when the element characteristic changes due to temperature fluctuation by detecting a change in the characteristic of the semiconductor element in operation and feeding back the detected result so as to correct the change of the characteristic. CONSTITUTION:Suppose that a threshold voltage Vt of a FET 1 is higher than a gate voltage Vg, the FET 1 is cut off. Then a voltage Vd is higher, an output voltage Vc of a buffer circuit is higher to apply feedback so as to lower the threshold voltage Vt of the FET 1. When the voltage Vt is lower than the voltage Vg, the FET 1 is conductive conversely. Since the current drive capability of the FET 1 is sufficiently larger than a current Io, the voltages Vd, Vc are lower to apply feedback thereby increasing the voltage Vt. Since FETs 1, 101 and 102 are mounted on one and same chip, the temperature of them is nearly equal to each other and the threshold voltage of each FET is nearly equal. Thus, the threshold voltage of each FET is always nearly equal to the gate voltage Vg.
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