![]() It is the time taken from applying the input to the output produced. It is the amount of noise voltage allowed at the input and it should not affect the output. It is the product of the voltage which is supplied and current needed to produce the output. Number of inputs and outputs connected to the gate, which does not affect the usual performance and does not degrade the voltage. Characteristics of TTL: Fan in and Fan out: To increase the number of inputs, the number of emitters at transistor Q1 is increased accordingly. Q3 and Q4 transistors together form the output. Transistor Q1 consists of 2 emitters, two inputs are given through this 2 emitters. It also consists of four resistors R1,R2,R3,R4 and a diode D. It consists of four transistors Q1,Q2, Q3 and Q4. This is the two input TTL NAND gate circuit. Internal Structure of 2 input NAND Gate TTL A simple 2-input AND gate can be constructed using RTL Resistor-transistor switches connected together as shown below with the inputs connected directly to the transistor bases. Consider the DTL gate circuit shown in Fig. The most important feature to note is that the input diode has been replaced by a transistor. Input Circuit of the TTL Gate Figure 14.9 shows a conceptual TTL gate with only one input terminal indicated. Internal structure and characteristics of standard TTL NAND gate: lowing how these problems are remedied in TTL. Logical ‘1’, input voltage required is 2V-5V.Logical ‘0’, input voltage required is 0V-0.8V.As the name suggests, the transistor performs two functions like logic as well as amplifying. Logical ‘1’, output voltage required is 2.4V-5V The Transistor-Transistor Logic (TTL) is a logic family made up of BJTs (bipolar junction transistors).Logical ‘0’, output voltage required is 0V-0.4V.Each method and IC has advantages and disadvantages.ĭepending upon the supply voltage which is given to the IC, the voltage required to ON and OFF or to make logic ‘1’ and ‘0’ changes. Depending upon the integration of Logic families the IC number changes. TTL Logic family ICs are in the series of 7400. Fast TTL Input and Output levels of TTL:.TTL is widely used because it is less expensive, more reliable and faster than the other digital logic families.ĭifferent types of Transistor- Transistor Logic are PN junction diode and resistors are also used in the integration of the chip. Transistor- Transistor Logic is made up of NPN and PNP transistor. The different types of integration of logic families are Resistor- transistor Logic (RTL), Diode- Transistor Logic (DTL), Transistor- Transistor Logic (TTL), Emitter coupled Logic (EML) and Complementary metal oxide Semiconductor Logic(CMOS). Each gate is integrated using different methods. The Logic gates which we use are manufactured using semiconductor devices like NPN and PNP transistors, Resistors, Diodes and FETs. However, transistor-transistor logic is still used in applications as they are fairly robust and the gates are relatively inexpensive.TTL and their characteristics Transistor- Transistor Logic (TTL): ![]() With the advent of CMOS, some applications using TTL have been supplanted by CMOS. ![]() Even with different transistor-transistor logic versions that are less current consuming, they are all still competitive to CMOS. Both transistors must be saturated ON for an output at Q. This circuit overcomes the limitations of the single transistor inverter. Notice that this circuit looks similar to those found in analogue push pull amplifiers, except that the transistors here. A simple 2-input AND gate can be constructed using RTL Resistor-transistor switches connected together as shown below with the inputs connected directly to the transistor bases. The heavy current demands of transistor-transistor logic can lead to improper functioning due to switching of output states. The schematic of a Transistor Transistor Logic (TTL) inverter is shown in figure 1. ![]() One major disadvantage of transistor-transistor logic is its high current consumption. Transistor-transistor logic is largely immune to damage from static electricity discharges, unlike CMOS, and are also relatively inexpensive compared to CMOS. Transistor-transistor logic has good “fan in” feature, meaning the number of input signals that can be accepted by an input. This is mainly due to good noise margins as well as guaranteed voltage levels. ![]() One of the biggest benefits of using transistor-transistor logic is the relative easiness in interfacing different circuits and the ability to produce complex logic functions. Advanced Schottky transistor-transistor logic.There are different sub-categories or families for transistor-transistor logic, such as: Techopedia Explains Transistor-Transistor LogicĪ transistor-transistor logic device makes use of transistors with multiple emitters in gates having multiple inputs. ![]()
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