Presentation on theme: "Digital CMOS Logic Circuits"— Presentation transcript:
1Digital CMOS Logic Circuits CMOS digital circuits:small sizeease of fabricationlow power dissipationCMOS Invertersedr42021_1004.jpgFigure (a) The CMOS inverter and (b) its representation as a pair of switches operated in a complementary fashion.
2Dynamic Operation of CMOS Inverter sedr42021_1006.jpgFigure Circuit for analyzing the propagation delay of the inverter formed by Q1 and Q2, which is driving an identical inverter formed by Q3 and Q4.
3sedr42021_1007a.jpgFigure Equivalent circuits for determining the propagation delays (a) tPHL and (b) tPLH of the inverter.
4Basic Structure of CMOS Logic Gate Circuits alternative circuit symbolssedr42021_1008.jpgFigure Representation of a three-input CMOS logic gate. The PUN comprises PMOS transistors, and the PDN comprises NMOS transistors.
5CMOS NOR Gatesedr42021_1012.jpgFigure A two-input CMOS NOR gate.
6CMOS NAND Gate sedr42021_1013.jpg Figure A two-input CMOS NAND gate.
7sedr42021_1014.jpgFigure CMOS realization of a complex gate.
8CMOS XOR Gate sedr42021_1015a.jpg Figure Realization of the exclusive-OR (XOR) function: (a) The PUN synthesized directly from the expression in Eq. (10.25). (b) The complete XOR realization utilizing the PUN in (a) and a PDN that is synthesized directly from the expression in Eq. (10.26). Note that two inverters (not shown) are needed to generate the complemented variables. Also note that in this XOR realization, the PDN and the PUN are not dual networks; however, a realization based on dual networks is possible (see Problem 10.27).
9Transistor Sizing sedr42021_1016.jpg Figure Proper transistor sizing for a four-input NOR gate. Note that n and p denote the (W/L) ratios of QN and QP, respectively, of the basic inverter.
10sedr42021_1017.jpgFigure Proper transistor sizing for a four-input NAND gate. Note that n and p denote the (W/L) ratios of QN and QP, respectively, of the basic inverter.