一、前言许多微电极放大器(缓冲级、探头级)使用只有一个场效应管的源极跟随器。采用恒流源使源极跟随器具有非常接近于1的增益。在这样的条件下,栅极与源极间电压的变化被减小,场效应管的实际栅源电容对输入电容的贡献极小。如果采用驱动式屏蔽能更进一步减小输入导线的电容。然而,由于场效应管栅源电容的存在,还是有几个微微法拉的输入电容。输入电容的更进一步减小,对于绝大多数记录情况似乎是不必要的。因为,为了进一步减小输入电容,特别要引起电路的复杂化,附加电路引起噪声增加,增大 I. INTRODUCTION Many microelectrode amplifiers (buffer stage, probe stage) use a source follower with only one FET. Using a constant current source causes the source follower to have a gain very close to one. Under such conditions, the change of the voltage between the gate and the source is reduced, and the actual gate-source capacitance of the FET contributes very little to the input capacitance. If the use of driven shielding can further reduce the input wire capacitance. However, due to the existence of the FET gate-source capacitance, there are still several pico-farads of input capacitance. A further reduction of the input capacitance seems unnecessary for the vast majority of recording situations. Because, in order to further reduce the input capacitance, especially to cause circuit complexity, additional circuits cause increased noise, increase