Automatic Gain Control Amplifier for Biomedical Applications

Abstract

70 percentage of power is consumed by analog front end of digital hearing aid system. Among them 30 percentage power is consume by pre amplifier and remaining by Analog to digital converter. Also noise limits the signal level and reduce the dynamic range. So, it is necessary to design low power low noise bio medical systems. To increase battery life, a low power dissipation method is very crucial. The purpose of an automatic gain control (A.G.C.) circuit is to maintain the output level of an amplifier, for example, at an almost constant value, even though its input signal level may change substantially. This work describes the design, implementation and simulations of low- noise and low power Pre Amplifier in 180 nm CMOS technology. The Pre Amplifier is used in the front-end of a hearing aid and its gain is digitally controlled based on input signal power level. In the AGC gain is changed by selecting different value of the capacitor. The final noise of the AGC is -98 db and the total Power dissipation of this AGC is 71 uw.The frequency used for this AGC is 1 KHz.when 30mv input signal is applied then 10pf value capacitor is on and final Gain is 25dB.when 10mv input signal is applied then first transmission gain on and 20pf capacitor is also on and Gain is 35dB. The aim of this project is to modify the gain , reduce the power and reduce the Noise with the help of different techniques. Using combinations of op-amp , comparator , VGA and digital to analog converter design fully AGC circuit and reduces noise and total Power dissipation of this AGC.