  Continuous-time Sigma-Delta (CT-$\Sigma\Delta$) modulators are oversampling
Analog-to-Digital converters that may provide higher sampling rates and lower
power consumption than their discrete counterpart. Whereas approximation errors
are established for high-order discrete time $\Sigma\Delta$ modulators,
theoretical analysis of the error between the filtered output and the input
remain scarce. This paper presents a general framework to study this error:
under regularity assumptions on the input and the filtering kernel, we prove
for a second-order CT-$\Sigma\Delta$ that the error estimate may be in
$o(1/N^2)$, where $N$ is the oversampling ratio. The whole theory is validated
by numerical experiments.
