| 摘要 |
PURPOSE:To exercise current control by using a bias circuit for a gate of an MOS transistor (TR) for load constituting a source follower section so that a power supply voltage fluctuation is coincident with the voltage fluctuation between G and S of an MOSTR for driving constituting the source follower section. CONSTITUTION:MOSTRs 63, 68 in the bias circuit 60 act like a constant current source through the combination of constant voltage sources 64, 70 and a constant current flows respectively to TRs 61, 71, and the G-S voltage of the TRs 61, 71 is always constant independently of the fluctuation of the power supply voltage between VDD and VSS. Thus, each voltage of circuit points 62, 69 becomes constant. An amplifier section 72 controls the gate of the TR67 so as to make the voltages of the circuit points 66, 69 equal to each other. Since the voltages of the circuit points 66, 69 are equal, the total sum of voltages at G-S of the TRs 61, 65 and 71 is equal to the power voltage between VDD and VSS. On the other hand, the total sum of the voltage of G-S of the TRs 31, 21 and 32 is equal to the power voltage between VDD and VSS. Further, when the ratio of the channel width to the channel length of the TRs 65, 67 and the TRs 21, 22 is made constant, the G-S voltage of the TR65 is equal to that of the TR21. Thus, the fluctuation of the power voltage is immune to the TRs 31, 32.
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