Fully coupled dynamic electro-thermal simulation on chip and circuit level is presented, Temperature dependent thermal conductivity of silicon is taken into account, thus solving the nonlinear heat diffusion equation, The numerical solution is carried out by using the industry-standard simulator SABER, therefore for electro-thermmal simulations we are able to use the common electrical compact models by adding a heatsource and thermal pins to them, The application of this technique and need for electro-thermmal simulation is illustrated with the simulation of a current control circuit built into a multiwatt package.