Low supply voltage, low noise fully differential programmable gain amplifiers

This paper presents the architecture, methodology, circuit design technique and measured results of a low voltage (2.6 V), fully differential, low-noise, programmable gain "microphone" amplifier, differential bandgap reference and low-voltage programmable gain "power" amplifier. They can be used in a low supply voltage analogue front-end for digital voice terminals. CMOS technology with 1.2 /spl mu/m channel length is used. The measured equivalent average input referred RMS noise voltage of the microphone amplifier is 5.1 nV//spl radic/(Hz) in the voice band at 40 dB closed loop gain. The power amplifier is capable of driving 50 /spl Omega/ load 200 mV from both supply voltages with distortions better than 0.5% under all conditions.