  We describe two experimental approaches to circumvent the problem of
self-heating in IV measurements on small mesa samples of 2212-BSCCO.
Simultaneous dc and temperature measurements have been performed, allowing
corrections for heating to be made. Short pulse measurements have also been
made, where the IV characteristics and the mesa temperature can be measured on
a $\mu $s time-scale enabling intrinsic IV characteristics to be derived, even
in the presence of appreciable self-heating. Self-heating leads to an
appreciable depression of the apparent energy gap and also accounts, in major
part, for the s-shaped characteristics often reported at high currents. By
correcting for the temperature rise, we derive the intrinsic temperature
dependence of the tunnelling characteristics for crystals with a range of
doping. Results are compared with recent theoretical models for c-axis
transport in d-wave superconductors.
