A Class of Minimum Sensitivity Amplifiers

The ease and low cost of fabricating large numbers of transistors in microelectronic configurations make feasible the use of redundant active devices to achieve improved reliability and decreased sensitivity to parameter changes. This paper considers an amplifier configuration which has particular advantages for microcircuit realization. The arrangement described is capable of yielding a fractional gain change which is equal to the product of the fractional deviations in the gains of each of the redundant signal channels. The nominal input-output transmission is maintained, with negligible changes in gain and bandwidth, even with complete failure of one or more (but not all) of the signal channels; this is achieved at the expense of an increase in sensitivity. The sensitivity to large parameter changes can be minimized over an appreciable portion of the amplifier passband by use of the systematic design procedure which is presented. Experimental verification of theoretical predictions and a design procedure are included.