Diode logic suffers from voltage degradation from one stage to the next. A circuit configuration or arrangement of the circuit elements in a special manner will result in a particular logic family. Transistor logic and then transistortransistor logic, dtl and ttl. Logic family conversion table to from ttl hct act hc ac hc, ac. Simple digital logic gates, like the and or the or. This makes schottky diodes an excellent choice for reverse protection diodes. The set of digital ics belonging to the same logic family are electrically compatible with each other 4. The flashiest member of the diode family must be the lightemitting diode. Lesson 1 voltage, current, resistance engineering circuit analysis. Diode logic dl diode logic dl is the most primitive of all the digital logic families.
Logic family logic families indicate the type of logic circuit used in the ic. Rtl was made from discrete transistors and resistors and manufactured on printed circuit boards with several gates per board. Need a resistor to limit base current many ics leave r l unconnected. Diodetransistor logic dtl was used in the ibm 608 which was the first alltransistorized computer. Diode logic pdf complete license key only permits the or and. An and gate is a logic circuit that only turns on an output when all the inputs are high or a logic state of 1. For example, suppose we wire up five diode resistor and gates in series. The families included here comprise of emitted coupled logic ecl, resistor transistor logic rtl, diode transistor logic dtl, transistor logic ttl, and diode logic dl. In fact, it combines diodes and resistors so sometimes it is known as dioderesistor logic drl. The ttl family is based on the bipolar junction transistor, and was the first commonly available series of logic elements. A family of diode logic and diodetransistor logic integrated circuits was developed by texas instruments for the d37c minuteman ii guidance computer in 1962, but these devices were.
In this article, you will find the study notes on logic families which will cover the topics such as integrated circuits, characteristics of digital circuits, logical families, digital ic terminology, dl, rtl, dtl and ttl. Remember that the diode conducts only when it is forward biased. It is called transistortransistor logic because both the logic gating function and the amplifying function are performed by transistors. Its not clear at all to me from this description how 2 diodes could improve the turnoff of the transistor base one in the transistor emitter might. Figure 1 shows the simplified circuit of a ttl device with diode inputs, such as are used with. For example, suppose we wire up five dioderesistor and gates in series. One basic thing about the diode, is that diode needs to be forward biased to conduct. Forward and reverse bias switch a diode between the low and high impedance states, respectively. 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. D provides a discharge path for stored base charge in the. Dtl offers better noise margins and greater fanouts than rtl, but suffers from low speed, especially in comparison to ttl.
Logic gates from resistors, diodes, and transistors. Integrated circuits integrated circuits ics are chips, pieces of semiconductor material, that contain all of the transistors, resistors, and capacitors. Since dl does not use active components such as transistors, it does not provide. The logic families which fall under the first kind are called bipolar families, this include diode logic dl, emitted coupled logic ecl, resistor transistor logic rtl, diode transistor logic dtl, transistor transistor logic ttl. The dioderesistor logic circuits consist of diodes and resistor only, the logic functions available are and, or, levelshifted and and levelshifted or. Bicmos family diode logic in dl diode logic, only diode and resistors are used for implementing a particular logic. Clamp diodes clamp dioded2x and d2y do nothing in normal. It is extremely simple and inexpensive because it only uses passive components. Logic families significance and types of logic families. In the bipolar category there are three basic families called, diode transistor logic dtl, transistor transistor logic ttl and emitter coupled logic ecl. Characteristics of logic families in digital electronics. Shortcircuit current and internal resistance of logic families.
Ee40 lec 18ee40 lec 18 diode circuitsdiode circuits. Rtl gates are now seldom used, if at all, in modern digital electronics design because it has several drawbacks, such as bulkiness, low speed, limited fan. In this video, details of diode and logic is discussed. Diode logic was used extensively in the construction of early computers, where semiconductor diodes could replace bulky and costly active vacuum tube elements. Early transistorized computers were implemented using discrete transistors, resistors, diodes and capacitors. Diode circuit analysis by assumed diode states 1 specify ideal diode model or piecewiselinear diode model id a id a reverse bias forward bias vd v reverse bias forward bias 2 each diode can be on or off vdon 3 circuit containing n diodes will have 2 n states 4 the combination of states that works for all di d i t t ith. Ttl transistortransistor logic families history and. Recall that, as long as the breakdown region of operation is avoided, the diode can be approximated as a voltage controlled switch that is closed for v d v on where the diode is on and open for v d 0, but blocks the ow i.
The most commonly used bipolar logic family is transistortransistor logic. 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. Diodes and diode circuits tlt8016 basic analog circuits 20052006 8 half wave rectifier with smoothing capacitor figure 3. A family of diode logic and diode transistor logic integrated circuits was developed by texas instruments for the d37c minuteman ii guidance computer in 1962, but these devices were. Digital logic circuits are manufactured depending on the specific circuit technology or logic families. Transistortransistor logic ttl is a class of digital circuits built from bipolar junction transistors bjt and resistors. Diode transistor logic dtl diode transistor logic, or dtl, refers to the technology for designing and fabricating digital circuits wherein logic gates employ both diodes and transistors. All you have to remember, is that current flows through a diode in the direction of the arrow. Diodetransistor logic 1 chapter 5 diode transistor logic resistortransistor logic was an early form of logic used in the 1950s and early 1960s. Background diode logic dl or diode resistor logic drl is a logic family that uses only diodes and the resistors in the implementation of the logic functions. As well as ttl and cmos technology, digital logic gates can also be made by connecting together diodes, transistors and resistors to produce rtl, resistortransistor logic gates, dtl, diodetransistor logic gates or ecl, emittercoupled logic gates but these are less common now compared to the popular cmos family. The piecewise linear approximation to diode circuit analysis is based on the diode model of the previous section. Diode logic dl resistor transistor logic rtl diode transistor logic dtl transistor.
Peak inverse voltage peak inverse voltage piv across the diode. Pdf diode transistor logic diode logic suffers from voltage degradation from one stage to the next. In fact, it combines diodes and resistors so sometimes it is known as diode resistor logic drl. Resistortransistor logic rtl resistortransistor 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. Ttl logic gates are rapidswitching devices the sn7400, for example, takes just 15 ns to change state.
Two diodes in series double the voltage, not lower it. Actually, there are many different ttl families, with a range of speed, power. There are various logic families namely 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 transistortransistor logic ttl cmos logic ttl and cmos logic family is most widely used ic. Discrete componentstransistor, diode, resistor, etc. And and or functions can be implemented using the diode logic very easily. We can use diodes to perform logical and operation. The other logic family is the mos family and this includes nmos, pmos, and cmos family. 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. Rtlresistor transistor logic dtldiode transistor logic ttltransistortransistor logic eclemitter coupled logic cmoscomplementary metal oxide semiconductor logic out of these rtl and dtl are rarely used. Ecl pmos and cmos dioderesistor logic resistortransistor logic directcoupled transistor logic. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. However, the following comments apply to all other bipolar logic families.
That means all the gates belonging to the bipolar family use the transistorised circuits. Diodetransistor logic dtl diodetransistor logic, or dtl, refers to the technology for designing and fabricating digital circuits wherein logic gates employ both diodes and transistors. The first kind of logic families is bipolar families. Diodes d1x and d1y and resistor r1 in figure ttl1 form a diode and gate, as in section diode. Digital logic family there are various logic families namely 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. Diodes can perform switching and digital logic operations. Let us investigate some of such circuits using diode. In this figure, if both inputs are left unconnected or are both at logic 0, output z will also be held at zero volts by the resistor, and will thus be a logic 0 as well. Two diodes in series are commonly used to lower the voltage and prevent any base current when one or more inputs are at low logic level. The first diode transistor logic family of integrated circuits was introduced by signetics in 1962. The bipolar families of logic circuits use the bipolar transistors fabricated on the chip.