| 摘要 |
PURPOSE:To prevent a current from leaking to the side of a power supply terminal when a resister is trimmed by connecting one end of the second diode of a third island region to the island electrode of a first island region, the other end to the power supply terminal and short-circuiting a Zener diode by applying a current thereto to break it. CONSTITUTION:Resisters R2 and R1 are formed in the same island region ISL1 and a Zener diode D1 and a diode D2 are formed in island regions ISL2 and ISL3, respectively. The electrode 12 of the resistor R2 is grounded and the other electrode 11 thereof is connected to the electrode 21 of the Zener diode and an external terminal T. The island terminal 13 of the island region ISL1 is connected to the cathode electrode 31 of the diode D2 and the anode electrode 32 thereof is connected to a higher power supply voltage Vcc. The Zener diode D1 and the diode D2 are formed by utilizing the base diffusion and emitter diffusion of semiconductor integrated circuits, respectively. Thus, the diode D2 becomes reverse-biased and the current of a constant current source Ic is prevented from leaking to a power supply. |
