As with the nchannel example, a logic signal from the system power management control circuitry turns the load switch on and off via a smallsignal nmos transistor, q1. Diode and transistor nand gate or dtl nand gate and nand. Nmos devices passes a strong 0 but a weak 1 while pmos transistors pass a strong 1 but a weak 0. Nov 08, 2017 problem on nmos pass transistor logic gate 2014 ece paper solution duration. Transistor level implementation of digital reversible circuits. A transistortransistor logic ttl not gate or inverter is one of the simplest logic gates used in digital electronics. This is a transistortransistor logic ttl and gate circuit using bipolar junction transistors. One of the first papers examining pass transistor logic and formalizing pass transistor design style was published by whitaker, in 1983 whitaker, electronics. The result is in some cases conceptual simplification, but the cmos inverters strict logic high logic low output characteristic is lost. Passtransistorlogic xor gate using pass transistor logic.
One of the first papers examining passtransistor logic and formalizing passtransistor design style was published by whitaker, in 1983 whitaker, electronics. Passtransistor logic ptl, also known as transmissiongate logic, is based on the use of mosfets as switches rather than as inverters. Pass transistor properties v vdd v t v vdd 2v t v vdd 3v t v v t v 2v t v 3v t this is bad. It realizes a logic function using nmos pass transistors with cmos restoring buffers. V s will initially charge up quickly, but the tail end of the transient is slow. The current drive of the transistor gate tosource voltage is reduce significantly as v. The ntype pass transistor can pass an input signal when a logic 1 is biased on the gate, and it is turned off when a logic 0 is biased on the gate. This technique uses the complementary properties of nmos and pmos transistors. This paper compares the use of complementary passtransistor logic cpl as more powerefficient than conventional cmos design. 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. Ttl is an acronym standing for transistortotransistor logic.
Mod01 lec15 pass transistor logic circuits ii duration. Transmission gate an overview sciencedirect topics. Complementary pass transistor logic a general method of karnaugh map coverage and mapping into circuit realizations is applied to design logic andnand, ornor, and xorxnor gates in cpl. Do not drive pass gate with a pass gate output along a long series chain quickly degrades outputs and eats into noise margin if vdd 3. The truth table of xor gate is as shown in table below. Pdf a new 5transistor xorxnor circuit based on the. Xor gate can be combined with the different logic gates to realize more complex gate functions that are used extensively in building blocks arithmetic logic circuits. Logic not gate tutorial with logic not gate truth table.
Other authors use the term complementary pass transistor logic cpl to indicate a style of implementing logic gates using dualrail encoding. A selfchecking cmos full adder in double pass transistor. This circuit uses a commonly available bipolar junction transistor bjt. Any logic expression can be imple mented by using cmos log ic family, which contains. If input is a and output is x then the expression for the output is xa. Introduction to passtransistor logic technical articles. And, or, not, nand not and, nor not or, xor xnor not xor 9 did you know.
Pchannel pass transistor circuit electrical model for the experiment with the pchannel pass transistor is shown in fig. Differential and passtransistor cmos digital circuits. Figure below shows the implementation of or function using nmos transistors only. In this configuration there are two transistors connected in series. Basic logic gates in cmos principles construct the nfet network using only nfets and the pfet network. A new 5transistor xorxnor circuit based on the pass transistor logic conference paper pdf available december 2011 with 3,561 reads how we measure reads. These four inputs construct an xor logic operation at the transistor level, which is designed using two transistors.
A basic circuit using any generalpurpose bipolar transistor such as the bc549, bc548, or bc547, can be used to construct the and gate. Pass transistor logic xor gate using pass transistor logic. For simplicity we will show here only two inputs nand gate circuit by using diodes and transistors. He was born in lincoln, england and he was the son of a shoemaker. Every cpl gate has two output wires, both the positive signal and the complementary signal, eliminating the need for inverters. Logic gates digital circuit that either allows a signal to pass through it or not. Digital logic gates nand and nor are called universal logic gate because we can construct all other logic gates using nand gate or nor gate alone. The method consists of the implementation of the gates. The method is general and can be extended to synthesize any passtransistor network. Also note that you can in theory, ymmv mix up pass transistor logic with pushpull logic. Cpl consists of complementary inputsoutputs, a nmos passtransistor network, and cmos output inverters 5. In a survey of low power circuit design we conc1uded that pass transistor logic. In this paper, we present a selfchecking full adder based on the double pass transistor technology. When both input a and b are given with 0 v, both of the diodes are in forward biased condition that is in on condition.
The paper describes how the logic functions can be efficiently and optimally built using passtransistor logic. That is, a low input 0 gives a high output 1, and vice versa. A general method in synthesis of passtransistor circuits. What is not gate inverter, not logic gate inverter circuit. The paper describes how the logic functions can be efficiently and optimally built using pass transistor logic. This method of realization of gate is called rtl resistor transistor logic. The result is in some cases conceptual simplification, but the cmos inverters strict logichighlogiclow output characteristic is lost. Area, delay and power dissipation have emerged as the major concerns of designers. Some logical circuits using ptl pass transistor logic october 9, 2012 8 9. Therefore it should be used wisely, and may eventually not be convenient. Pass transistor logic f product term control signal pass signal v p. A simple 2input logic not gate can be constructed using a rtl resistortransistor switches as shown below with the input connected directly to the transistor base.
Cmosbased carbon nanotube passtransistor logic integrated. Oct 09, 2012 pass transistor logic october 9, 2012 7 8. Gate circuits constructed of resistors, diodes and bipolar transistors as illustrated in this section are called ttl. Basic logic gates in cmos principles construct the nfet network using only nfets and the pfet network using only pfets. A transistor transistor logic ttl not gate or inverter is one of the simplest logic gates used in digital electronics. Nmos devices passes a strong 0 but a weak 1 while pmos transistors pass a. Using transistors as logic gates electrical engineering.
The transmission gate logic is used to solve the voltage drop problem of the pass transistor logic. This circle is known as an inversion bubble and is used in not, nand and nor symbols at their output to represent the logical operation of the not function. Cpl consists of complementary inputsoutputs, a nmos pass transistor network, and cmos output inverters 5. Pass transistor logic ptl, also known as transmission gate logic, is based on the use of mosfets as switches rather than as inverters. Used to build logic functions there are seven basic logic gates.
Pdf a new 5transistor xorxnor circuit based on the pass. Transistors are used as switches to pass logic levels between nodes of a circuit, instead of as switches connected directly to supply voltages. It shows some fundamental pass transistor building blocks which became. This paper compares the use of complementary pass transistor logic cpl as more powerefficient than conventional cmos design. Implementation of low power cmos full adders using pass. Jun 21, 2012 mod01 lec14 pass transistor logic circuits i. The standard not gate is given a symbol whose shape is of a triangle pointing to the right with a circle at its end. In this gate if the b input is high the right nmos is turned on and copies logic 1 to f and this operation does not affected by a input. 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 order to reduce the number of transistors, the output of the xor gate a. 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 the process technology level 1. Logic not gates are available using digital circuits to produce the desired logical function. Logic gates digital circuit that either allows signal to pass through it or not used to build logic functions seven basic logic gates.
For a ttl input, r2 should probably be about 3 or 4 times the value of r3, e. Transmissiongate digitalcmosdesign electronics tutorial. Ratioed logic pass transistortransmission gate logic dynamic cmos logic domino npcmos. Diode and transistor nand gate or dtl nand gate and nand gate. Or gate using pass transistor logic the truth table of or gate is as shown in table below. 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. Passtransistor logic switch network a b b reduced number of transistors no static power consumption. The gate delay depends on the capacitive load of the gate. 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. Digital integrated circuits combinational logic prentice hall 1995 combinational logic. Not gate may be made using connect of one transistor and two resistor as shown in fig. It should be noted that although transmissiongate based and passtransistor based designs can reduce silicon area, placing a pass transistor on a normal signal path could lead to difficulty in testing, because a highimpedance state is introduced at the output of the pass transistor when the pass transistor is. Static cmos circuit at every point in time except during the switching. In electronics, pass transistor logic ptl describes several logic families used in the design of integrated circuits.
Complementary passtransistor logic a general method of karnaugh map coverage and mapping into circuit realizations is applied to design logic andnand, ornor, and xorxnor gates in cpl. Complementary pass transistor logic gates with balanced input loads in andnand circuit, fig. A not gate using a transistor is very simple to make. Mod01 lec14 pass transistor logic circuits i youtube. Logic gates a b out 0 0 0 0 1 1 1 0 1 1 1 1 a b out 0 0 0. Jul 25, 2018 realizing nand gate using diode and transistor. Mar 31, 2018 the output of not gate is represented by a a bar. It should be noted that although transmission gate based and pass transistor based designs can reduce silicon area, placing a pass transistor on a normal signal path could lead to difficulty in testing, because a highimpedance state is introduced at the output of the pass transistor when the pass transistor is stuck at the off state.
Double passtransistor 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. The transistor must be saturated on for an inverted output off at q. Figure below shows the implementation of xor function using pass transistors. Pdf 123 decision diagram is a very effective ptl synthesis tool based on binary decision diagram.
It reduces the count of transistors used to make different logic gates, by eliminating redundant transistors. A selfchecking cmos full adder in double pass transistor logic. The current drive of the transistor gatetosource voltage is reduce significantly as v. Problem on nmos pass transistor logic gate 2014 ece paper solution duration. 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 the process technology level. Cpl is a static gate, because outputs are connected to vdd or gnd through a. B is fed through an not gate from the differential node to the pass transistors as a control input. And, or, not, nand not and, nor not or, xor, and xnor not xor later building functions. In this gate if the b input is low then left nmos transistor is on and the logic value of a is copied to the output f. This is a transistor transistor logic ttl and gate circuit using bipolar junction transistors. When en is low, q1 is off and the gate is pulled up to vin. When en is high, q1 turns on, the pass transistor gate is pulled to ground, and the. Apply to the circuit in figure 2 the voltages listed in table 2, and observe and record the voltage v o at the output of the pass transistor.
Complementary pass transistor logic or differential pass transistor. Pdf transistor level implementation of digital reversible. An inverter, or not, gate is one that outputs the opposite state as what is input. This nand gate is called dtl nand gate or diode transistor logical nand gate. Single transistor pass gate with v t 0 out v dd v dd 5v v dd 0v 5v 0v watch out for leakage currents. Nand gate can be built using 4 mosfets 2nmos and 2pmos. 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. One of the key steps in the use of transmission gates and pass transistors for logic implementation is the identification of pass variables to replace the 1. In fact, this type of a switch is often used in digital and analog circuits, but it is not an and gate. Though it has high speed due to low input capacitance, it has limited capacity to drive a load.
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