Analog front-end for microphones used in audio applications

Low noise amplifier working under low power supply is a popular and necessary cell in many electronic devices, for example, the audio microphone commonly requires a low noise preamplifier to boost the weak input signal without introducing much noise. This project is dealing with the design of such an amplifier using 0.18μm CMOS technology in Cadence Virtuoso. A two-stage folded cascode topology is chosen with the constant transconductance biasing structure. Using wide swing current mirror and Sooch configuration, the biasing circuit is able to work stably and own a high input and output range. To stabilize the high frequency performance, the cascode compensation or ‘Ahuja’ compensation technique is used. Various op amp specifications are met such as the high open loop gain of 87dB, unity gain bandwidth of 10MHz, phase margin of 53deg and gain margin of 15dB. Used in the microphone application, it achieves a loop gain of 50dB, high phase margin of 85deg. The total input referred noise level, SNR, THD, SFDR, SNDR will be also studied and explained to evaluate the microphone noise performance.Bachelor of Engineerin