Based on the pre-amplifier array, an average resistor network was designed to reduce voltage offset. The causes of boundary effect of resistance network were analyzed. Redundant pre-amplifier design and ring average network design are adopted, and unequal termination resistance design is proposed to alleviate the boundary effect. The node matrix current equation was proposed. It could provide the optimization direction for the design of average resistance network. After the boundary effect improved by using the node matrix current equation design, using the pre-amplifier array in a 12-bit folding-interpolation ADC, the ENOB is 1032 bits and the SFDR is 743 dB at a sampling frequency of 25 GSPS and a 08 V sinusoidal input of 1242 GHz.