Anne bracy cs 3410 computer science cornell university the slides are the product of many rounds of teaching cs 3410 by professors weatherspoon, bala, bracy, and sirer. Cmpen 411 vlsi digital circuits spring 2012 lecture 07. Cmos and pass transistor logic 2 institute of microelectronic systems nchannel transistors produce a logic 0 at the output when a logic 1. Vlsi began in the 1970s when complex semiconductor and communication technologies were being developed. The complex transmission gate came into picture because of the undesirable threshold effects of the simple pass transistors. Hello and welcome original pdf to todays lecture on passtransistor logic circuits this is the page replacement policies pdf second. Pdf 123 decision diagram is a very effective ptl synthesis tool based on binary decision diagram. Microelectronic systems vlsi design of integrated circuits 4. Transmission gate gives good non degraded logic levels. Figure below shows implementation of and function using only nmos.
Introduction the increasing demand for lowpower very large scale integration vlsi can be addressed at different design levels, such as the architectural, circuit, layout, and. This technique uses the complementary properties of nmos and pmos transistors. In the field of very large scale integration vlsi, adders are used as the basic component from processors to asics. Anna university regulation 2017 ece ec8095 vlsi d notes, vlsi design lecture handwritten notes for all 5 units are provided below. Mos transistor switches pswitch a b s p a b s s 1 s 0 good 1, poor 0 1 0 1 0 degraded a b s s cmos switch a b s c s 0 s 1 a good 0 good 1 transmission gate b s s 4 signal strength strength of signal how close it approximates ideal voltage source v dd and gnd rails are strongest 1 and 0 nmos pass strong 0. From transistorsto logic gates and logic circuits prof. As the mos devices are wide spread, there is high need for circuits which consume less power, mainly for portable devices which run on batteries, like laptops and handheld computers. It reduces the count of transistors used to make different logic gates, by eliminating redundant transistors. Ec8095 vlsi d notes, vlsi design notes ece 6th sem. Passtransistor dual value logic for lowpower cmos the increasing prominence of portable systems and the need to limit power consumption in very high density vlsi chips have led to rapid and innovative developments in. Vlsi design pass transistor logicpass transistor logic adapted from rabaeys digital integrated circuits, 2002, j.
The pass transistor logic is required to reduce the transistors for implementing logic by using the primary inputs to drive gate terminals, source and drain terminals. Switches and switch logic can be formed from simple n or p transistors and from the complementary switch i. Domino logic characteristics only noninverting logic very fast only 1 0 transitions at input of inverter affects the next domino static inverter increases noise immunity, increase the size of pmos to increase v m proper sizing of inverter to drive the fanout in optimal way add a levelrestoring transistor to overcome. Im just trying to help a classmate understand the lectures note from a class. In complementary cmos logic primary inputs are allowed to drive only gate terminals.
In electronics pass transistor logic ptl describes several logic families used in the design of integrated circuits. Performance penn ese 570 spring 2018 khanna 2 pass transistor logic penn ese 570 spring 2018 khanna teaser. But there are some circuits which are made using other logics like pass transistor logic, dynamic cmos logic etc. Download link for ece 6th sem vlsi design notes are listed down for students to make perfect utilization and score maximum marks with our study materials ec8095 vlsi design objectives. Logic gates in cmos indepth discussion of logic families in cmosstatic and dynamic, pass transistor, nonran tioed and ratioed logic n optimizing a logic gate for area, speed, energy, or robustness lowpower and highperformance circuitdesign techniques 6.
Static cmos circuit at every point in time except during the switching transients each gate output is connected to either v dd or v ss via a lowresistive path the. Cmos logic gates, pass transistor logic department of electrical and computer engineering. For the love of physics walter lewin may 16, 2011 duration. Mos transistors duke electrical and computer engineering. Bec logic comes from the lesser number of logic gates than the full adder fa structure.
Cpeee 427, cpe 527 vlsi design i pass transistor logic. The basic dynamic logic gateconcept is shown at left top the pass transistor mp is an nmos device, but could also be implemented with a transmission gate tg c x represents the equivalent capacitance of the input gate of the second nmos device part of an inverter or logic gate as well as the. Combinational logic gates in cmos purdue engineering. Vlsi design pass transistor logicpass transistor logic. The current drive of the transistor gatetosource voltage is reduce significantly as v. Though it has high speed due to low input capacitance, it has limited capacity to drive a load. Pass transistor pt logic a b f b 0 a 0 b a b b f a b.
Vlsi design notes pdf vlsi pdf notes book starts with the topics basic electrical properties of mos and bicmos circuits, logic gates and other complex gates, switch logic, alternate gate circuits, chip level test techniques, systemlevel test techniques, layout design for improved testability. Nmos is effective at passing a 0, but poor at pulling a node to vdd. Then leap which is singlerail passtransistor logic then differential. Dynamic logic circuits pusat pengajian kejuruteraan. Cmos and pass transistor logic solution suggestions 4. Digital integrated circuits combinational logic prentice hall 1995 combinational logic.
It realizes a logic function using nmos pass transistors with cmos restoring buffers. A selfchecking cmos full adder in double pass transistor. Remember nmos transistors pass a strong 0 but a weak 1. Vec i tno tn increases of pass transistor due to body effect v sb v gs. A general method in synthesis of passtransistor circuits d. Hello and welcome to todays lecture on passtransistor logic circuits. A methodology for synthesis of passtransistor functions was established presenting a modified karnaugh map which employs the pass variables, not only logic zeroes and ones.
Or, inv b implement the circuit as a complexgate c compare the transistor count. In the last couple of lectures we have discussed how boolean functions can be realized by using static. Hi, these videos are not a study guide nor am i an expert. This video is highly rated by electronics and communication engineering ece students and has been viewed 437 times. A general method in synthesis of passtransistor circuits. Evaluate the design of differential cascode voltage switch with pass gate dcvspg. In this paper, we present a selfchecking full adder based on the double pass transistor technology. Nmos inverter for any ic technology used in digital circuit design, the basic circuit element is the logic inverter.
Design and implementation of carry select adder with pass transistor logic rajani katneni 1. If something on pdf slides does not look ok, please try reading them with acrobat 4. In this paper the 123 decision diagram is applied to realize cmos pass. Double pass transistor logic dpl the basic difference of pass transistor logic compared to the cmos logic style is that the source side of the logic transistor networks is connected to some input signals instead of the power lines. In fact, this type of a switch is often used in digital and. It is a cmos based switch, in which pmos passes a strong 1 but poor 0, and nmos passes strong 0 but poor 1. Differential and passtransistor cmos digital circuits.
Disadvantage that output levels are always lower than the input level. Advanced digital integrated circuits lecture notes and video archive. Vlsi design 2 verylargescale integration vlsi is the process of creating an integrated circuit ic by combining thousands of transistors into a single chip. Cmos transistor theory cmos vlsi design slide 31 pass transistors qwe have assumed source is grounded qwhat if source 0. V s will initially charge up quickly, but the tail end of the transient is slow. Implementation of low power cmos full adders using pass. Transistor level implementation of digital reversible circuits. Though these comprise a small part of the vlsi circuit it is necessary to understand them. It shows some fundamental pass transistor building blocks which became very popular in vlsi design practices. Design and implementation of carry select adder with pass. Nmos devices passes a strong 0 but a weak 1 while pmos transistors pass a. Milenkovic 3 pass transistor logic 9182006 vlsi design i. Here we demonstrate that a significant reduction in the use of fieldeffect transistors can be achieved by constructing carbon nanotubebased integrated circuits based on a. A transmission gate tg is an analog gate similar to a relay that can conduct in both directions or block by a control signal with almost any voltage potential.
Vlsi design notes pdf vlsi pdf notes book starts with the topics basic electrical properties of mos and bicmos circuits, logic gates and other complex gates, switch logic, alternate gate circuits, chip level test techniques, systemlevel test techniques, layout design for. Xor has the worstcase karnaugh mapif implemented from simple gates, it requires more transistors than any other function. The transmission gate logic is used to solve the voltage drop problem of the pass transistor logic. Ratio gate counttransistor count is roughly 110 ic logic gates fall under ssi, combinational logic circuits fall under msi, and microprocessor system come under lsi and vlsi. Pass transistor logic, and performance penn ese 570 spring 2018 khanna lecture outline. Pass transistor logic adapted from rabaeys digital integrated circuits, second edition, 2003 j. Most of the logic in digital vlsi circuits is made using cmos logic because of its low power consumption, high fanout. Milenkovic 6 nmos transistors in seriesparallel primary inputs drive both gate and sourcedrain terminals nmos switch closes when the gate input is high remember nmos transistors pass a strong 0 but a weak 1 ab xy x y if a and b xy a b x. Once the operation and characterization of an inverter circuits are thoroughly understood, the results can be extended to the design of the logic gates and other more complex circuits. Pass transistor logic often uses fewer transistors, runs faster, and requires less power than the same function implemented with the same transistors in fully complementary cmos logic.