The influence of bootstrap and neutral beam driven currents on the loop voltage, the toroidal current density and the ideal ballooning stability in ASDEX L- and H-mode plasmas is investigated by computer simulations. It is found that the loop voltage computed with neoclassical resistivity and Ohmic, bootstrap and beam driven currents comes close to the measurement. Bootstrap currents of up to 100 kA with broad profiles are generated. The field diffusion due to the driven currents is assessed by inclusion of these currents in the diffusion equation for the poloidal magnetic field. The main effect is the adjustment of the total current density to the broader electrical conductivity profiles in the H-phase on the resistive diffusion time-scale of about 400 ms. The broadening due to bootstrap and beam driven currents is comparatively small, so that the ideal ballooning stability is left almost unchanged. In the pre-transition L-phase and in the H-phase the plasma is stable, whereas at the beta limit it is marginally stable to ideal ballooning modes.