Digital Electronics: Principles, Devices and Applications

170 Digital Electronics+VDDA+VDDA – A – AB – BB –Y=(AB+AB)BABFigure 5.54 Example 5.8.SolutionThe given circuit can be divided into two stages. The first stage comprises two inverters that produceA and B. The second stage is a two-wide, two-input AND-OR-INVERT circuit. Inputs to the firstAND are A and B, and inputs to the second AND are A and B. The final output is therefore given byY =AB + AB, which is an EX-NOR function.5.6 BiCMOS LogicThe BiCMOS logic family integrates bipolar and CMOS devices on a single chip with the objectiveof deriving the advantages individually present in bipolar and CMOS logic families. While bipolarlogic families such as TTL and ECL have the advantages of faster switching speed and larger outputdrive current capability, CMOS logic scores over bipolar counterparts when it comes to lower powerdissipation, higher noise margin and larger packing density. BiCMOS logic attempts to get the bestof both worlds. Two major categories of BiCMOS logic devices have emerged over the years sinceits introduction in 1985. In one type of device, moderate-speed bipolar circuits are combined withhigh-performance CMOS circuits. Here, CMOS circuitry continues to provide low power dissipationand larger packing density. Selective use of bipolar circuits gives improved performance. In the other