In general, {HEAD ~ transistors} used in circuitry are designed to have {TAIL ~ this optimum concentration} 
are designed to have
In general , { HEAD ~ transistors } used in circuitry are designed to have { TAIL ~ this optimum concentration }
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL