  Spectral approach to the charge carrier transport in $p-n$-junctions has
allowed us to revise the theoretical results relating to large signal operation
of the junction to make them valid for both the low and high frequencies
ranges. The spectral composition of the external circuit current includes both
the DC and AC components. The former produces the static current--voltage
characteristic with the modified Bessel function of zeroth order, $I_0(\beta
V_\sim)$, while the latter yields the dynamic admittance with the modified
Bessel function of first order, $I_1(\beta V_\sim)$, either of them depend on
the signal amplitude. Our experimental results are consistent with the
theoretical ones if a fitting parameter allowing for recombination processes in
the depletion layer is taken into account.
