The circuit consists of an npn transistor and a zener diode. A hybrid cmos logic style adder with 22 transistors is reported 7. Figure below shows implementation of and function using only nmos. Transistors now that we know about diodes, lets put two of them together, as follows. Vlsi design cmos process parameters exam study material. Feb 27, 2017 problem on nmos pass transistor logic gate 2014 ece paper solution duration. Cmpen 411 vlsi digital circuits spring 2011 lecture 07.
Digital integrated circuits combinational logic prentice hall 1995 overview static cmos conventional static cmos logic ratioed logic pass transistor transmission. Diode logic dl resistor transistor logic rtl diode transistor logic dtl emitter coupled logic ecl logic families can be classified broadly according to the technologies they are built with transistor transistor logic ttl cmos logic ttl and cmos logic family is most widely used ic technologies. Oklobdzija electrical and computer engineering department university of california. Logic design department of electrical engineering, iit bombay.
From switches to transistors, logic gates and logic circuits hakim weatherspoon cs 3410, spring 20. Pass transistors transistors can be used as switches 6. Transistors in gates design ed by pass transistor logic ar e less than the number of transistors utilized in cmos logic design. Complementary pass transistor logic a b a b b a b a b. A general method in synthesis of passtransistor circuits. It realizes a logic function using nmos pass transistors with cmos restoring buffers. Basic pass transistor logic model f sum of products control signals pass signals v i p.
It is a simple matter to design a series pass voltage regulator circuit like this. Ptl uses a nmos or pmos transistor to transfer charge from input node to the output node, under the control of gate voltage. A logic family of monolithic digital integrated circuit devices is a group of electronic logic gates constructed using one of several different designs, usually with compatible logic levels and power supply characteristics within a family. If we put a small current into one of the terminals, called the base, then the switch is oncurrent may flow. And finally, i shall discuss about the logic synthesis by using pass transistors. Wave form result of both cmos logic and pass transistor logic output wave form of cmos carry skips adder conventional fig5a and b proposed carry skip adder output wave form using nmos pass transistor logic. Lecture 24 mosfet basics understanding with no math reading. Pass transistors require lower switching energy to charge up a node, due to the reduces voltage swing. The outputs of the gates assume at all times the value. Bipolar junction transistors emitter p n collector base pnp transistor emitter n p base npn transistor bipolar. Combinational logic gates in cmos purdue engineering. Logic circuits adapted from cmos logic circuit design by john p. From transistorsto logic gates and logic circuits prof. Basic pass transistor logic model f sum of products control signals pass signals v i p i 1 1 2 2 n n.
Amitava dasgupta, department of electrical engineering,iit madras. Vlsi design cmos process parameters exam study material for. 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 outputs of the gates assume at all times the. As shown in the figure below, the collector and emitter terminals of the transistor are in series with the load. A general method in synthesis of passtransistor circuits d. When the input to the base resistor is 5v the base current is 8ma and turns on the transistor putting 11. At first glance, this looks like an insulator but the actual behavior is far more interesting, if we apply external voltages properly n n p collector emitter base moderately doped. As demonstrated in the preceding section, ptl is built around mosfet switches that either pass hence the name or block a signal. Lean integration with pass transistors leap, 1996 all exploit pass transistors to implement general logic functions 22feb02 e4. In complementary cmos logic primary inputs are allowed to drive only gate terminals. The advantage is that one passtransistor network either. Ratioed logic pass transistor transmission gate logic dynamic cmos logic domino npcmos.
Xorxnor ptl cell with 16 transistors is reported in 4. When using a transistor as a switch most of the time its ok to ignore the 0. Then leap which is singlerail pass transistor logic then differential. Mos transistors silicon substrate doped with impurities adding or cutting away insulating glass sio 2 adding wires made of polycrystalline silicon polysilicon, poly or metal, insulated from the substrate by sio 2 drain source gate n n drain source gate sio 2 insulator ptype doped substrate drain source gate nmos transistor. Designing pass transistor logic circuits 10ff, c2 50ff the following circuit shows a general function block to realize boolean gates using pass transistor logic, such that both charging and discharging paths exist. 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. Pass transistor logic f product term control signal pass signal v p if 1 if 0 v p z p f. Alan doolittle lecture 24 mosfet basics understanding with no math reading. Input a is applied to an ntype pass transistor, and input b is applied not only to the ptype pass transistor, but also to the common gate of these two pass transistors. Transmission gate gives good non degraded logic levels. Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures, nptel online courses, youtube iit videos nptel courses. For example, the diode in the dtl can be replaced by a transistor whose collector is pulled up to the power supply.
From power dissipation graph it can be observed that the pass transistor logic dissipates larger power when compare to cmos, gdi and mgdi, it is due to the reduced output swings due to the threshold drop across a singlechannel pass transistor. Hello and welcome original pdf to todays lecture on pass transistor logic circuits this is the page replacement policies pdf second. Digital integrated circuits combinational logic prentice hall 1995 combinational logic. Gate is static a lowimpedance path exists to both supply rails under all circumstances.
Accordin g to equation 1 with decreas e in number of transistors. From transistors to gates to logic circuits logic gates from transistors truth tables. Xor has the worstcase karnaugh mapif implemented from simple gates, it requires more transistors than any other function. Low power vlsi circuits and systems usb media storage type. In this paper, we present a selfchecking full adder based on the double pass transistor technology. Pass transistor logic adapted from rabaeys digital integrated circuits, second edition, 2003 j. Lecture 24 mosfet basics understanding with no math. Gate diffusion input logic gdi 4 567 is a special case of pass transistor logic that uses both nmos and pmos pass transistors. Lowpower 1bit fulladder cell using modified pass transistor logic n. Full adder design with 10 transistors using xorxnor gates is also reported in 6.
A differential double pass transistor logic unit citeseerx. The control gates are biased in a complementary manner so that both transistors are either on or off. Pass transistor outline pass transistor characteristics transmission gate logic some examples delay, power and noise characteristics full adder using transmission gate logic complementary pass transistor logic cpl other pass transistor logic families. At first glance, this looks like an insulator but the actual behavior is far more interesting, if we apply external voltages properly n n p collector emitter base moderately doped lightly doped, and very thin heavily doped.
Vlsi design pass transistor logicpass transistor logic adapted from rabaeys digital integrated circuits, 2002, j. Electronics nptel online videos, courses iit video. In this booklet, we shall use simple analytical models for mos transistors. Gate preparation, nptel video lecture dvd, electronicsandcommunicationengineering, vlsidesign, cmosprocessparameters, nmos transistors, pmos transistors, mos. This paper compares the use of complementary pass transistor logic cpl as more powerefficient than conventional cmos design. Logic network employs input signals at both gate and drain terminals. The output remains in high impedance state when gate voltage is zero. Mos transistors silicon substrate doped with impurities adding or cutting away insulating glass sio 2. Pass transistor outline pass transistor characteristics transmission gate logic some examples delay, power and noise characteristics full adder using transmission gate logic complementary passtransistor logic cpl other passtransistor logic families. Ajit pal, computer science and engineering, iit kharagpur.
Figure1 portrays the schematic representation of a basic. Ece 261 james morizio 33 at every point in time except during the switching transients each gate output is connected to either v dd orv ss via a lowresistive path. O c t o b e r 9 t h, 2 0 1 7 pass transistor logic 2. When the voltage on node a is a logic 1, the complementary logic 0 is applied to node activelow a, allowing both transistors to conduct and pass the signal at in to. This paper compares the use of complementary passtransistor logic cpl as more powerefficient than conventional cmos design. Goals for today from switches to logic gates to logic circuits transistors, logic gates, truth tables. Verilog coding, metal oxide seminconductor field effect transistor mosfet, fabrication process and layout design rules, propagation delays in mos, power disipation in cmos circuits, semiconductor memories. Pdf gatediffusion input gdi a technique for low power. Logic gates in cmos indepth discussion of logic families in cmosstatic and dynamic, passtransistor, nonran tioed and ratioed logic n optimizing a logic gate for area, speed, energy, or robustness lowpower and highperformance circuitdesign techniques 6. Oct 09, 2012 pass transistor logic october 9, 2012 7 8. The evolution from diode transistor logic to transistor transistor logic can be seen by observing the placement of pn junctions. Ttl logic family digital logic families electronics tutorial. 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. For pass transistor logic the number of transistor occupied is lesser than cmos and greater than gdi.
Some logical circuits using ptl pass transistor logic october 9, 2012 8 9. The complex transmission gate came into picture because of the undesirable threshold effects of the simple pass transistors. A selfchecking cmos full adder in double pass transistor logic. In electronics, pass transistor logic ptl describes several logic families used in the design of integrated circuits. Nptel online videos, courses iit video lectures well organized. Pmos or nmos is sufficient to implement the logic function, which results in smaller number of. Switches and switch logic can be formed from simple n or p transistors and from the complementary switch i. In electronics pass transistor logic ptl describes several logic families used in. In contrast to static cmos primary inputs drive gate terminals. P517617 lec 5, p7 transistors transistors are the heart of modern electronics replaced vacuum tubes voltage and current amplifier circuits high frequency switching computers impedance matching low power small size, can pack thousands of transistors in mm2 in this class we will only consider bipolar transistors. The output node charges from 0 v ddv tn, and the energy drawn from the power supply for charging the output of a pass transistor is given by c l. Vlsi design pass transistor logicpass transistor logic.
Static cmos circuit at every point in time except during the switching. This solidstate switch is comprised of a pmos transistor and nmos transistor. 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. Knowing the maximum current required by the load, it is possible to calculate the maximum emitter current. Cmpen 411 vlsi digital circuits spring 2012 lecture 07. In computer engineering, a logic family may refer to one of two related concepts. Introduction to passtransistor logic technical articles.
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