| 摘要 |
PURPOSE:To obtain a constant current source suitable for a differential amplifier through its excellent saturation characteristic only by connecting the output of a voltage generator which gives a reverse bias to a substrate which is intrinsically comprised for the other object to the gate of depletion type IGFET. CONSTITUTION:When an output of a voltage generator GEN for reversely biasing a substrate is applied to the gate of IGFETQ2S for constant current, the constant current region spreads and when a gate voltage is set to a negative value f, a drain current ID is saturated by a low drain voltage. In addition, when a threshold voltage of depletion type IGFET is set low (absolute value is large), a current is no longer sensible to a change of gate voltage and thereby a constant current can be obtained easily. Moreover, since an output of GEN is connected to the substrate, only connection of the gate of a constant current IGFETQ2S to the substrate is required and particular wiring on the IC surface is no longer necessary. Therefore, it is particularly advantageous for the provision of plurality of constant current IGFET's within an IC. Such device can also be adopted to a P channel type IC where a substrate voltage is positive. |
