Improved Current Mirror Accuracy Without Extra Semiconductor Devices
Original Publication Date: 1985-Aug-01
Included in the Prior Art Database: 2005-Feb-19
This circuit provides resistive compensation at the reference branch of a current mirror which increases the potential applied to the output branch of the current mirror by an amount sufficient to offset the imbalance between the reference current and the desired output current. The imbalance is caused by the diversion of base current from the collector of the input transistor. In the prior art, an additional device has been used to reduce the base current error to the order of the reciprocal of the square of the current gain. Figs. 1A and 1B illustrate two well known techniques for reducing the base current error. In each case Q3 is added to reduce the base current error in Q1 and Q2, and thus the error in output current Io .