Investigating noise reduction capabilities in CMOS pre-amplifier circuits

This paper presents the design of low noise CMOS pre-amplifiers. Phone IC is one of the applications that pick-up voice signal from a microphone and the preamp amplifies to audible signal. Normally when the sound signal is very weak the amplifier amplifies signal as well as noise. This may result an amplified sound with low signal to noise ratio (SNR). A simulation study has been conducted to compare the noise characteristic of Claus' and Eduard's CMOS preamp design. The simulations were conducted by using SIMUCAD SmartSpice, mainly to analyze the gain of those design circuits, besides the input signal and noise spectral density for the SNR analysis. The result then is used to improve the SNR of CMOS based operational amplifiers and finally facilitate the actual design work of pre-amp using 0.18μm CMOS Technology.