preamplifier 13 capacitors c b are selected to minimize power line noise in terms of noise performance and number of external components needed the protection circuit 11 u2032 in fig2 b is preferable to the protection circuit 11 of fig2 a however in case of a semiconductor failure protection circuit 11 completely blocks any dc flow to the electrodes and tissues as opposed to reducing the dc flow below an acceptable threshold in preferred embodiments band pass amplifier 2 has a single ended output architecture while a differential output can be used in the context of the invention and may provide enhanced performance significant area and power penalties must be paid to achieve those benefits gain programmability may be achieved as shown in fig2 a and 2 b by using switches that select different combinations of resistors to vary the ratios of r 3 to r 4 the gain of preamplifier 13 in the recording band may be fixed and given by the ratio 1 r 1 r 2 in preferred embodiments the high pass filtering stages are implemented with g m c filters since precision in the poles is not crucial the closed loop transfer function of the low pass amplifier amp 1 may be set to have its dominant pole at 9 khz for 5 u03bcv peak input neural signals while providing the necessary further gain such dc gain is given by the ratio 1 r 3 r 4 the dc restoration stage 17 may comprise a g mo c o high pass filter preferably with an input linear range higher than 0 2 v precision again is not crucial since this stage is only needed for compensation of the band pass amplifying.