对于一个理想的模拟开关,它的导通电阻 R_(ON)应为零,关断电阻 R_(OFF)为无穷大,但在实际器件中,总存在着一定的导通电阻和关断电阻。如 CC4066B 型四双向模拟开关,导通电阻 R_(ON)大约在200Ω至1000Ω左右。由于这个电阻的存在,使开关的输出电压不等于输入电压,在输出端产生了误差。在精度要求比较高的电路中,这种误差是不能忽视的。本文介绍一种比较可行的电路,可使导通电阻趋向于零。模拟开关在导通时的等效电路如图1所示,图中R_S 即模拟开关的导通电阻。由于 R_S 的存在,使输出电压不等于输入电压,即 For an ideal analog switch, its on-resistance R_ (ON) should be zero and its turn-off resistance R_ (OFF) is infinite, but there are always on-resistance and turn-off resistance in real devices. Such as CC4066B type four bidirectional analog switch, the on-resistance R_ (ON) is about 200Ω to 1000Ω or so. Due to the existence of this resistor, the output voltage of the switch is not equal to the input voltage, resulting in an error at the output. In the circuit with high accuracy requirements, this error can not be ignored. This article describes a more viable circuit, the on-resistance tends to zero. The equivalent circuit of the analog switch when it is on is shown in Figure 1, where R_S is the on-resistance of the analog switch. Due to the presence of R_S, the output voltage is not equal to the input voltage, that is