transfer function 1 a zero 1 z u2212 1 has been inserted at a half of the sampling frequency to reduce the quantization noise at high frequency after some simple mathematical calculations the previous transfer function 2 becomes yout y 1 1 z u2212 1 u2212 y 2 1 u2212 z u2212 1 y 2 z u2212 2 1 u2212 z u2212 1 3 in this way the transfer function provides the sum of three terms the signals y 1 and y 2 are signals that can have only two values for this transfer function implementation delays are implemented by means of flip flops and sign inversions that can be realized by inverters in addition there are circuits that are able to realize the function 1 u2212 z u2212 1 like that reported in fig3 in fig3 there is shown an operational amplifier 30 that provides an output voltage vout which has a capacitor c 1 applied between its inverting input and its output the non inverting input is connected to a prefixed bias voltage vp 1 at the inverting input a terminal of a switch 36 is also connected and the other terminal is connected to a terminal of.