In this paper the discretization of switched and
non-switched linear positive systems using Padé approximations
is considered. We show:
1) first order diagonal Padé approximation preserves both
linear and quadratic co-positive Lyapunov functions,
higher order transformations need an additional condition
on the sampling time1;
2) positivity need not be preserved even for arbitrarily small
sampling time for certain Padé approximations.
Sufficient conditions on the Padé approximations are given to
preserve positivity of the discrete-time system. Finally, some
examples are given to illustrate the efficacy of our results
