Switched-Capacitor-Filters: A Comparison and Some Experimental Results

Switched-Capacitor-Filters are a very powerful and promising approach for the fully monolithic integration of filter functions. Different realization concepts are compared with respect to passive and active component count, as well as their sensitivity properties. The comparison of different signalflow- graph simulations with sampled-data integrators, the simulation of RC-active filter sections and the new concept using voltage inverter switches proposed by Fettweis yields a number of advantages for this last concept: Lower opamp number, lower sensitivity and no restrictions on the clock frequency because of the application of the bilinear frequency transformation. Measured results on a discrete, simple test-filter with voltage inverter switches are in agreement with the calculated values.