| 摘要 |
PURPOSE:To output a current with high accuracy even in the case of a minute current by providing a voltage holding circuit holding the terminal voltage of a current input terminal on the input terminal of a switching circuit switching a constant current. CONSTITUTION:Respective certain fixed bias voltages are applied to respective gate terminals of constant current transistors(TR) 1, 4 and constant current outputs depending on these bias voltages are attained. These constant current outputs are outputted to the current output terminal 5 by turning on any side of switching TRs 2, 3. In such a case, the TRs 2, 3 are controlled by inputting control signals to respective gate terminals 10, 11 and both TRs are not turned on simultaneously. Thus, each output current of the TR 1 when the TR 2 is turned on and the TR 4 when the TR 3 is turned on is outputted to the terminal 5. At this time, capacitors 6-9 with enough larger capacity than the parasitic capacity of drain terminals 12, 13 hold the drain and the source voltages of the TRs 2, 3 to roughly the same potential. Thus, the current with high accuracy is attained even in the case of the minute current. |
