输入电阻ri是放大器的主要动态参数之一,测量ri几乎是模拟电子学实验中必然安排的内容。查阅了不少院校的电子学教材、电子学实验指导书,输入电阻几乎都是通过输入回路串入电阻R(如图1)进行测量,具体方法如下:当开关K断开(R接入)时,测得U_s和U_i值,则可用下式求得输入电阻 The input resistance ri is one of the main dynamic parameters of the amplifier. The measurement ri is almost an inevitable arrangement in analog electronics experiments. Access to many institutions of electronic materials, electronic experiment guide, the input resistance are almost all through the input circuit into the resistor R (Figure 1) to measure, as follows: When the switch K off (R access ), Measured U_s and U_i value, you can find the input resistance using the following formula