设计中PGA281作为第一级放大衰减电路，单端输入，差分输出，控制增益为1时，VOCM引脚悬空，输入交流正弦信号，输出信号峰峰值等于输入信号峰峰值，但有一个非常大的直流分量。输入直流电压时输出电压确有衰减，非常不解，把VOCM引脚接地，输出没有直流分量了，但峰峰值衰减为输入的0.5，此时设置的倍数仍为1呀，望指导，在线等，PGA281部分原理图见附件
The output signal is fully differential around the common-mode voltage (VOCM). The VOCM input pin is typically
connected to the midsupply voltage in order to offer the widest signal amplitude range. VOCM is a highimpedance input that requires an external connection to a voltage within the supply boundaries. If the VOCM pin is left floating, the output common-mode voltage is undefined, and the amplifier will not operate properly. The usable voltage range for the VOCM input is specified in the Electrical Characteristics and must be observed.
