  The proposed delta-sigma modulator ($\Delta\Sigma$M) based signal acquisition
architecture uses a differential difference amplifier (DDA) customized for dual
purpose roles, namely as instrumentation amplifier and as integrator of
$\Delta\Sigma$M. The DDA also provides balanced high input impedance for signal
from sensors. Further, programmable input amplification is obtained by
adjustment of $\Delta\Sigma$M feedback voltage. Implementation of other
functionalities, such as filtering and digitization have also been
incorporated. At circuit level, a difference of transconductance of DDA input
pairs has been proposed to reduce the effect of input resistor thermal noise of
front-end R-C integrator of the $\Delta\Sigma$M. Besides, chopping has been
used for minimizing effect of Flicker noise. The resulting architecture is an
aggregation of functions of entire signal acquisition system within the single
block of $\Delta\Sigma$M, and is useful for a multitude of dc-to-medium
frequency sensing and similar applications that require high precision at
reduced size and power. An implementation of this in 0.18-$\mu$m CMOS process
has been presented, yielding a simulated peak signal-to-noise ratio of 80 dB
and dynamic range of 109dBFS in an input signal band of 1 kHz while consuming
100 $\mu$W of power; with the measured signal-to-noise ratio being lower by
about 9 dB.
