The crosstalk in a multi-element photoconductor is one of the factors which have influences on the performance of a system. The electronic crosstalk caused by ground resistance can be reduced by increasing bias resistance. According to the characteristics of a HgCdTe photoconductive detector, a preamplifier with a constant current bias circuit is designed. The operation principle and noise of the circuit are analyzed. The noise model of the circuit is given. An expression for its equivalent input noise is derived. Finally, the circuit is implemented and its noise performance is tested.