Logic families logic families are sets of chips that may implement different logical functions, but use the same type of transistors and voltage levels for logical levels and for the power supplies. Transistor and logic gates laboratory instruction today you will learn how to use a transistor to amplify a small ac signal as well as using it as a switch to construct digital logic circuits. Actually, there are many different ttl families, with a range of speed, power consumption, and other characteristics. A particular characteristic of ttl signals is that. This is pretty far from any voltage that would be recognized as logic 0. The input to a ttl circuit is always through the emitters of the input transistor, which exhibits a. Transistor transistor logic 1 chapter 6 transistor transistor logic the evolution from dtl to ttl can be seen by observing the placement of pn junctions.
Transistortransistor logic university of st andrews. Studying the internal connection of and, or, nand and nor. Transistortransistorlogic topics the most commonly used bipolar logic family is transistortransistor logic. Introduction to computer engineering csece 252, fall 2012 prof.
On the use of complementary pass transistor logic for design of dpa resistant circuits. From switches to transistors, logic gates and logic circuits hakim weatherspoon cs 3410, spring 20 computer science cornell university. Transistor logic switches, also known as transistor transistor logic ttl became widespread after the invention of the bipolar junction transistor bjt. Ttl family the logic family refers to the general physical realization of a logical element, such as the ttl, emittercoupled logic ecl, or complementary metaloxide semiconductor cmos. The equivalent resistance of all the resistors connected to logical 1 and the equivalent resistance of all the. Nmos transistor g g connect source to drain when v g v supply g n. To find the advantages of this family over dtl family. When the be junction is forwardbiased, transistor is on. We will conclude this chapter by looking at how transistors can be used as logic devices. Digital electronics and logic circuits role of transistors. This is a transistortransistor logic ttl and gate circuit using bipolar junction transistors.
Resistor transistor logic rtl watch more videos at lecture by. Rtl was made from discrete transistors and resistors and manufactured on printed circuit boards with several gates per board. Over previous technologies, ttl had speed and reliability. Experiment 6 transistortransistor logic ttl gates objectives be familiar with the transistor transistor logic ttl circuits. If any of the three inputs is high, corresponding transistor is driven into saturation resulting in low output.
From switches to transistors, logic gates and logic circuits hakim weatherspoon cs 3410, spring 20. Logic gates from resistors, diodes, and transistors. Zion fanout the fanout of a logic gate is the number of inputs that the gate can drive without exceeding its worstcase loading specifications. Box 5969, 60 safat, kuwait a new fault model that incorporates both logic and circuit level description is presented. 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.
The circuit examples in this section are based on a representative ttl family, lowpower schottky ls or lsttl. One of the prominent features of transistor transistor logic signals is the ability of the inputs of the gate rise to the logical 1 if left unconnected. Fanout must be examined for both possible output states. For example, the diode d2 from figure 2 in the chapter on dtl can be replaced by a transistor whose collector is pulled up to the power supply. Introduction to computer engineering csece 252, fall 2012. These families vary by speed, power consumption, cost, voltage. Transistor logic switches, also known as transistortransistor logic ttl became widespread after the invention of the bipolar junction transistor bjt. Since an integrated circuit is constructed primarily from dozens to even millions of transistors formed from a single, thin silicon crystal, it. In the case of both devices, we will talk about the nonlinear models, load line analysis and applications. Indeed, the bulk of digital systems applications employing ssi and msi packages were designed using ttl. This is a logic family which is mainly build up of npn transistors, pn junction diodes and diffused resistors.
Transistortransistor logic ttl a common semiconductor technology for building discrete digital logic integrated circuits. Diodetransistor logic dtl is a class of digital circuits that is the direct. If the input impedance of the transistor circuit is too low then it will load the previous one, reducing the signal level and possibly causing distortion in some instances. Ttl transistortransistor logic families history and. Transistors in the circuit of a computer microprocessor can switch on and off thousands of times per second. Without the invention of the transistor, computer processing power would be very limited and slow. Unit overload protected logic level power mosfet in a 3 pin plastic surface vds continuous drain source voltage 50 v mount envelope, intended as a id continuous drain current. Nov 21, 2012 ttltransistor transistor logic slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Transistor amplifiers transistor has 3 legs, one of them is usually grounded. A transistor fault model for nmos combinational circuits. 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. Basic semiconductor physics, diodes, the nonlinear diode model, load line analysis, large signal diode models, offset diode model, transistors, large signal bjt model, load line analysis, small signal model and transistor amplification. This will lead naturally to our discussion of digital systems.
Ismaeel department of electrical and computer engineering, college of engineering and petroleum, university of kuwait, p. 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. Transistors and logic circuits transistor control voltage in voltage out control high allows current to flow switch is closed on control low stops current flow switch is open off 2 not gate one transistor in out in high, switch is closed so current flows to ground out is low. What are the advantages of ttl transistor transistor logic.
Next we will talk about diodes, followed by the bipolar junction transistor. Mar 15, 2020 the full form of ttl is transistor transistor logic. Nchannel logic level enhancement mode field effect transistor general description these nchannel enhancement mode field effect transistors are produced using on semicondcutors proprietary, high cell density, dmos technology. Transistor transistor logic gate electronics tutorials.
Ttl input or output lead is defined to be positive if the. Check our section of free ebooks and guides on transistor circuits now. Comparable rise and fall times under the appropriate relative transistor sizing conditions. Ttl, or transistortransistor logic, is a digital circuit that uses multiple transistors to derive its output. Transistor transistor logic topics the most commonly used bipolar logic family is transistor transistor logic. Diodes and transistors university of california, berkeley. The full form of ttl is transistor transistor logic. Individual transistors still cost money in the 1960s.
This page contains list of freely available ebooks, online textbooks and tutorials in transistor circuits. Resistor transistor logic rtl watch more videos at comvideotutorialsindex. Free transistor circuits books download ebooks online textbooks. Cpl is a static gate, because outputs are connected to vdd or gnd through a low resistance path high noise resilience. Shortcircuit current and internal resistance of logic families. Rtl is the earliest class of transistorized digital logic circuit used. Diodetransistor logic dtl is a class of digital circuits that is the direct ancestor of transistortransistor logic. 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. Vbe, and if a logic high is applied to the input, current flows into the base of transistor q3 via transistors q1 and q2, which switches. Bss8 nchannel logic level enhancement mode field effect. A transistor is a threeterminal device that establishes a lowresistance path between two terminals when a high voltage is placed on the. Resistortransistor logic rtl sometimes also transistorresistor logic trl is a class of digital circuits built using resistors as the input network and bipolar junction transistors bjts as switching devices.
The selection comes from experience you know this will work as you point out other values would work too. With any of the input at logic low, corresponding emitter base junction is forward biased and the voltage drop across the base of q1 is around 0. Understanding transistor circuit design electronics notes. To solve the problem with the high output resistance of the simple output stage the second schematic adds to this. So logic was done with basic common emitter or common collector config. When you switch off this lower half, this pull down transistor as well as.
Resistor values in transistor logic gates electrical. If a string of inputs are logic 0 and the series diodes are conducting, then the output from the final stage should be recognized as a logic 0 as well. The first family of transistors, sylvania universal highlevel logic suhl, was produced. Resistor transistor logic rtl resistor transistor logic, or rtl, refers to the obsolete technology for designing and fabricating digital circuits that employ logic gates consisting of nothing but transistors and resistors. A switching transistor could perform the logic function and the amplifying function, which changed the digital electronics industry overnight. Older logic technologies used simple transistor configurations. Delay a function of load capacitance and transistor on resistance. Its name signifies that transistors perform both the logic function the first transistor and the amplifying function the second transistor. It is called so because the logic gating function e. In the pnp transistor the emitter is made from ptype material, the base is ntype. Ttl and cmos characteristics purpose logic gates are classified not only by their logical functions, but also by their logical families. Configuring a transistor stage to provide the right input impedance is a key element of the electronic circuit design process. Transistor transistor logic circuits basic ttl inverter basic dtl invertercompare basic ttl nand gate actual ttl nand gate vtc.
Diode logic va vout and vcc vb gate va vout or gate vb n diode logic suffers from voltage degradation from one stage to the next. Diode logic dl resistortransistor logic rtl diodetransistor logic dtl emitter coupled logic ecl logic families can be classified broadly according to the technologies they are built with transistortransistor logic ttl cmos logic ttl and cmos logic family is most widely used ic technologies. Standard ttl logic inverter model 2 r l i l t computer engineering technology g. Free transistor circuits books download ebooks online. Resistortransistor logic rtl is a class of digital circuits built using resistors as the input. We shall begin this section with a study of the evolution of ttl from dtl. Calculate the base current of a bipolar npn transistor having the bias voltage 10v and the input base resistance of 200k.
A bipolar junction transistor is formed by joining three sections of semiconductors with alternatively di erent dopings. Experiment 6 transistors as amplifiers and switches. Pass transistor logic attempts to decrease the quantity of transistors necessary to realize the logic by allowing the principal inputs to drive gate terminals radhakrishnan 1985 as well as drainsource terminals. This is a transistor transistor logic ttl and gate circuit using bipolar junction transistors. Politecnico di milano applications of resistortransistor logic in. Diode transistor logic 1 chapter 5 diode transistor logic resistor transistor logic was an early form of logic used in the 1950s and early 1960s. It overcomes the main problem associated with dtl, i. Transistortransistor logic article about transistor. Transistor logic and then transistortransistor logic, dtl and ttl. This type of bipolar transistor configuration is a non inverting circuit in that the signal voltages of. Transistor basics emitter to base junction is forward biased normally collector to base junction is reverse biased normally transistors are current operated devices, so kcl should be applied first. The middle section base is narrow and one of the other two. Pdf the emergence and proliferation of smart cards and other securitycentric.
Passtransistor logic attempts to decrease the quantity of transistors necessary to realize the logic by allowing the principal inputs to drive gate terminals radhakrishnan 1985 as well as drainsource terminals as shown in figures 5. The basic building block of this logic family is nand gate and there are various subfamilies of this logic gate those are standard ttl, advanced schottky ttl, schottky ttl, low power ttl, high power ttl, fast ttl etc. Logic gates digital circuit that either allows a signal to pass through it or not. Dec 05, 2016 transistor transistor logic ttl is a class of integrated circuits which maintain logic states and achieve switching with the help of bipolar transistors. Chapter 5 diode transistor logic resistortransistor logic was an early form of logic used in the 1950s and early 1960s. Introduction the ta will show you the emitter, base and collector for the transistor. The on resistance of a mosfet is proportional to 1k.
Transistor logic and then transistor transistor logic, dtl and ttl. An electrical device that can switch between low resistance and very high resistance is called a transistor, as we will see in sections b. The state of a bjt is not known before we solve the circuit, so we do not know which model to use. Ifvce v, the be junction is forward biased while bc junction is reversedbiased and transistor is in. It is called transistortransistor logic because both the logic gating function and the amplifying function are performed by transistors. Transistortransistor logic ttl transistortransistor logic, or ttl, refers to the technology for designing and fabricating digital integrated circuits that employ logic gates consisting primarily of bipolar transistors. Nikon ttl is the nikon camera companys version of the processing. Transistortransistor logic 1 chapter 6 transistortransistor logic the evolution from dtl to ttl can be seen by observing the placement of pn junctions. Diodetransistor logic dtluniversity of connecticut 56 2. Experiment 6 transistors as amplifiers and switches our final topic of the term is an introduction to the transistor as a discrete circuit element. Ic positive nor gate using resistance transistor logic. Guri sohi computer sciences department university of wisconsin madison.
Output transist or q4 is again switched off, causing the output voltage to rise to the value of vcc. Chapter 3 digital logic structures slides based on set prepared by gregory t. Transistortransistor logic ttl is a logic family built from bipolar junction transistors. A transistor fault model for nmos combinational circuits asad a. Transistor q1 actually behaves as cluster of diodes placed back to back. Figure 3 gives the circuit of a 3input positive nor gate using resistance transistor logic rtl with fan out of 5. A basic circuit using any generalpurpose bipolar transistor such as the bc549, bc548, or bc547, can be used to construct the and gate. In any implementation of a digital system, an understanding of a logic elements physical capabilities and limitations, determined by its logic family, are critical to proper operation. Diodes and transistors pdf 28p this note covers the following topics. Two basic examples of simple transistor driven logic and or circuits are shown below. Calculate the base current ib to switch a resistive load of 4ma of a bipolar npn transistor which having the current gain. Resistor transistor logic rtl sometimes also transistor resistor logic trl is a class of digital circuits built using resistors as the input network and bipolar junction transistors bjts as switching devices.