van der Donk A G, Bergveld P
University of Twente, Electrical Engineering, The Netherlands.
J Acoust Soc Am. 1992 Apr;91(4 Pt 1):2261-9. doi: 10.1121/1.403660.
A theoretical noise analysis of the combination of a capacitive microphone and a preamplifier containing a metal-oxide-semiconductor field-effect transistor (MOSFET) and a high-value resistive bias element is given. It is found that the output signal-to-noise ratio for a source follower and for a common-source circuit is almost the same. It is also shown that the output noise can be reduced by making the microphone capacitance as well as the bias resistor as large as possible, and furthermore by keeping the parasitic gate capacitances as low as possible and finally by using an optimum value for the gate area of the MOSFET. The main noise source is the thermal noise of the gate leakage resistance of the MOSFET. It is also shown that short-channel MOSFETs produce more thermal channel noise than longer channel devices.
给出了对电容式麦克风与包含金属氧化物半导体场效应晶体管（MOSFET）和高值电阻偏置元件的前置放大器组合的理论噪声分析。发现源极跟随器和共源电路的输出信噪比几乎相同。还表明，通过使麦克风电容和偏置电阻尽可能大，并且进一步通过使寄生栅极电容尽可能低，最后通过使用MOSFET栅极面积的最佳值，可以降低输出噪声。主要噪声源是MOSFET栅极泄漏电阻的热噪声。还表明，短沟道MOSFET比长沟道器件产生更多的热沟道噪声。
