RB-Compensated Current Mirror
by Dennis L. Feucht
Innovatia Laboratories
An inverting current amplifier, or current mirror, is shown below.
Input current, II, is amplified and is output as IO.
This current mirror topology has been used in IC design to improve two-transistor
current-mirror accuracy by adding a base resistor, RB, usually
implemented monolithically as a pinch resistor. More applicable to discrete
designs using a matched pair of transistors and accurate emitter resistors,
one additional non-accurate resistor of the right value can improve mirror
accuracy by over an order of magnitude.
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