In the embodiment disclosed, {TAIL ~ clipping} may be achieved by means of a diode 162, 164 and 166 provided in parallel with the corresponding reference resistor 146, 152 and 158 in each of {HEAD ~ the respective stages} 114, 116 and 118 
In the embodiment disclosed , { TAIL ~ clipping } may be achieved by means of a diode 162 , 164 and 166 provided in parallel with the corresponding reference resistor 146 , 152 and 158 in each of { HEAD ~ the respective stages } 114 , 116 and 118
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH