A mode selection amplifier circuit has multiple differential amplifier circuits coupled to receive input signals A, B and C. Each differential amplifier circuit is selectively operable for generating a signal output representative of an output mode with the output mode of each differential amplifier circuit selected from one of algebraic combinations of the signal inputs A-C, B-C, A-B and (A+B)/2-C. The mode selection amplifier circuit is usable in a signal acquisition probe for providing various signal output modes to a measurement test instrument.