What the designer should know infineon technologies. Complementary passtransistor logic 7 consists of complementary inputsoutputs, a nmos passtransistor network, and cmos output inverters. The series pass resistor will have to carry a heavy load when the load current increases. In the configuration above, the transistor is referred to as a pass transistor. Transistors are used as switches to pass logic levels between nodes of a circuit, instead of as switches connected directly to supply voltages. 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. The circuit consists of an npn transistor and a zener diode. Experiment 6 transistors as amplifiers and switches. Differential and passtransistor cmos digital circuits. In fact, this type of a switch is often used in digital and. 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 circuit design techniques 6. Current to voltage converter transimpedance amplifier see analog engineers circuit cookbook. Therefore, vfos made from bipolar transistors tend to drift more than jfets. Alan doolittle lecture 24 mosfet basics understanding with no math reading.
Introduction to passtransistor logic technical articles. Because of the current amplifying properties of the bjt in the ef. This work was further extended and formalized in markovic, oklobdzija, microelectronics. Design considerations and trends for high powersupply rejection psr. A formal design procedure for pass transistor switching circuits was developed later in whitaker, jo ssc. For example let us analyze a simple pass transistor circuit shown in fig. Similarly, the hybrid pass logic with static cmos output drive full adder hpsc was proposed by zhang et al. When a transistor is used primarily not as an amplifier but as an analog gate which controls the current flowing through it, it is called sometimes series pass transistor.
Pass transistor pt logic a b f b 0 a 0 b a b b f a b gate is static a lowimpedance path exists to both supply rails under all circumstances n transistors instead of 2n no static power consumption ratioless bidirectional versus undirectional. Differential cascade voltage switch logic dcvsl example. Pass transistor logic switch network a b b reduced number of transistors no static power consumption. A commonly used compound device is known as the darlington configuration and is shown to the right a modified version of figure 8.
In complementary cmos logic primary inputs are allowed to drive only gate terminals. Decision diagrams and pass transistor logic synthesis. Lecture 24 mosfet basics understanding with no math. Transistor series regulator since q 1 is an npn transistor, v o is found as. A general method in synthesis of passtransistor circuits. Remember nmos transistors pass a strong 0 but a weak 1. On pass transistor logic design computer science csu. At an earlier point, 3 transistors were omitted in our design and the number of transistors of the full adder cell was reduced to 17 transistors, which is lower than the number of transistors in the circuit described by markovic 8 which is 22. Pass transistor logic ptl, also known as transmissiongate logic, is based on the use of mosfets as switches rather than as inverters. Opamps can often be used as voltage comparators if a diode or transistor. If you decide to use the circuit in figure 1, be sure to heat sink q1 and q2. Discrete transistor circuits 197 audio circuits 202 simple active. Pullup circuit corresponds to pullup graph 11 21 graph models a b c gnd d a b d c pulldown circuit. Ombura project report submitted in partial fulfillment of the requirement for the award for the degree of bachelor of science in electrical and electronics engineering of the university of nairobi 2016.
The output of an n mos pass network is restored to achieve the maximum voltage swing at the output node, as well as low rise and fall times. Article pdf available in ieee journal of solidstate circuits 316. Lm339 data sheet national semiconductor pdf lm393 data sheet national semiconductor pdf lm311 data sheet national semiconductor pdf note. Pdf topdown passtransistor logic design researchgate.
The purpose of this book is to help the reader to understand how transistors work and how to design a simple transistor circuit. Since an integrated circuit is constructed primarily from dozens to even millions of transistors formed from a single, thin silicon crystal, it might be interesting and instructive to. In order for a pnp pass element to conduct current, the input voltage must be greater than the veb of the transistor. If load resistance increases, load voltage also increases.
Since the zener voltage is constant, the increase in v o causes v be to decrease. Pass transistors require lower switching energy to charge up a node, due to the reduces voltage swing. Mos transistors silicon substrate doped with impurities adding or cutting away insulating glass sio 2. Complementary passtransistor logic 7 consists of complementary inputs outputs, a nmos passtransistor network, and cmos output inverters. A general method in synthesis of passtransistor circuits d. We can map the bdd of f to a pass transistor circuit with. The humble transistor q1 emitter e collector c base b transistor basics emitter to base junction is forward biased normally collector to base junction is reverse biased normally transistors are current operated devices, so. In such hpsc circuit, xor, and xnor functions were simultaneously generated by pass transistor logic module by using only six transistors, and employed in cmos module to produce f. Npn linear regulators conventional linear regulators use npn bipolar transistors as the pass element.
The relative increase in base current lowers the transistors gain, ic ib, and the transistor is said to be in sa turation, symbol sat. A selfchecking cmos full adder in double pass transistor. Hi, these videos are not a study guide nor am i an expert. The exact current gain or hfe of the two transistors is not important since the regulator will increase or decrease the current through the pass transistors to maintain a constant output voltage. Darlington circuit to provide improved performance and inputoutput characteristics, single transistors may be combined to form compound devices.
This causes the series pass transistor to get bulky with a bulkier heat sink. In this paper, we present a selfchecking full adder based on the double pass transistor technology. When the external circuit does not allow the transistor to pass its full value of collector current, the current difference is a dded to the base current. Im just trying to help a classmate understand the lectures note from a class. Combinational logic gates in cmos purdue engineering. The configuration shown above is called an npn transistor. Page 2 of 3 20111229 r1 feedback continued the circuit in figure 2 provides better regulation than the simple emitter follower regulator. Fig 1 shows the full adder circuit using 17 transistors 9. This paper compares the use of complementary passtransistor logic cpl as more powerefficient than conventional cmos design. We can view the complementary cmos gate as switching the output pin to one of power or. The decrease in v be reduces conduction through the pass transistor. 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. The method is applied voltage of nmos rransistor, output signals have to be to pncrution of brs1c.
Logic synthesis for large pass transistor circuits premal buch amit narayan a. Pdf a general method in synthesis of passtransistor circuits. A classic example is a linear voltage regulator ldo in which a transistor controls the current which produces the output voltage. Pn junctions change their characteristics with temperature.
Pass transistors produce degraded outputs transmission gates pass both 0 and 1 well 4 7. Emitter, collector and base in its essence, a transistor consists of two diodes arranged back to back. Hello and welcome original pdf to todays lecture on pass transistor logic circuits this is the page replacement policies. The voltage drop across the current sense resistor can be compensated for as long as there is sufficient voltage drop across the series pass. Some logical circuits using ptl pass transistor logic october 9, 2012 8 9.
It reduces the count of transistors used to make different logic gates, by eliminating redundant transistors. Complementary passtransistor logic cpl, 1990 double passtransistor logic dpl, 1993 lean integration with pass transistors leap, 1996. Figure below shows implementation of and function using only nmos. Vlsi design pass transistor logicpass transistor logic. Consider the contents of this book as the first mile of a long journey into transistor circuits. Usually the pass element is composed of a pnp base current driver transistor and a single npn power transistor, therefore the. A car radio transmitters to use in the home, need a ham radio power supply dc12v or high current. As shown in the figure below, the collector and emitter terminals of the transistor are in series with the load.
The terminal on the left is called the emitter, the terminal on the right is. The result is in some cases conceptual simplification, but the cmos inverters strict logichighlogiclow output characteristic is lost. Lowvoltage lowpower logic styles, pass transistor logic, vlsi circuit design. Lecture 11 2 recent development in ptl new development by designers at hitachi japan in the last 6 years. Similarly, even though a pnp transistor is a currentdriven device, the emittertobase voltage veb of a pnp pass element is derived from the input voltage. In electronics, pass transistor logic ptl describes several logic families used in the design of integrated circuits. Experiment 6 transistors as amplifiers and switches our final topic of the term is an introduction to the transistor as a discrete circuit element. It is addressed to amateur circuit designer with little or no previous knowledge on semiconductors. Operational amplifiers opamps such as lm324, lm358 and lm741 cannot be used directly in many voltage comparator circuits. Driver card schema, pcb drawings and proteus isis simulation power transistors have cooler connects to the drive through. From switches to transistors, logic gates and logic circuits hakim weatherspoon. This module is devoted to the design of a transistor amplifier and this involves choosing the values of.
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