Precise Current Mirror
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
The current mirror circuit shown in the figure is designed for use on semiconductor integrated circuits. The function of a current mirror circuit is to generate a mirror current IM which is an exact copy of a reference current IR. The measure of the accuracy of a current mirror circuit is how closely the mirror current equals the reference current. Resistors R1 and R2 are of identical geometry and are in close proximity so that their resistance values are equal and track very closely. Transistors Q1 and Q2 are of identical geometry and are in close proximity so that their base-emitter voltage characteristics and current gains are equal and track very closely, and likewise for transistors Q3 and Q4.