FIXED_CURRENT_REGULATOR

Published:2009/7/17 3:26:00 Author:Jessie | From:SeekIC

This ftxed 1-mA current source delivers a ftxed current to a load connected between Q1's collector and ground; the load can be anywhere in the range from 0 Ω to 14 Ω. The circuit is powered from a regulated 15-V supply, and the R1/R2 voltage divider applies a 14-V reference to R3. The op amp's output automatically adjusts to provide an identical voltage at the junction of R4 and R5. That produces 1 V across R5, resulting in an R5 current of 1 mA. Because that current is derived from Q1's emitter, and the emitter and collector currents of a transistor are almost identical, the circuit provides a fixed-current source. The output current can be doubled by halving the value of R5.



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