of for example u00b1 0 5 microa the first transconductance amplifier t1 this has a transconductance k 1 charges an external storage capacitor 26 c stor to a storage voltage where p is the complex frequency according to the storage voltage v c the third transconductance amplifier t 3 this has a transconductance k 3 generates a correction current which is added in an summer 21 to for example a control current i con0 which takes account of the production tolerances and then forms the demodulator control current the control current i con0 can also serve for balancing the filter 222 a first 241 and a second 242 multiplier hereby multiply the control current i con0 in the normal mode by a factor k 1 from the equations 1 2 5 and 7 through 9 one can obtain by appropriate translation the corrected free running state frequency typical values are k d 1 f s 920 khz c int c nom 10 pf i con i con0 f 1 f s v 1 v ref c stor 1nf the limit frequency in the balancing loop lies at 20 hz in order to avoid audio signals creating distortions in the correction current i cor the correction current i cor can be advantageously exploited also for tuning the filter 222 for example by employing.