When designing a radiationhardened cmos system circuit, devices which use nand gates are more tolerant than those with nor gates. Cmos complexgate applications, and has been shown 6 to be the fastest static. Gate 2003 ece comparision of logic families dtl, cmos, ecl. As a result, there are very definite limits on the fanout of ttl or cmos outputs driving ttl inputs. Still, commercial ecl families arent nearly as popular as cmos and. Greenred productions relaxing music recommended for you. 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 value of the boolean function, implemented by the circuit in contrast, a dynamic circuit relies on temporary. Pdf an analytical model for calculating the propagation delay time of. Effectively, these symbols represent the fact that we are now considering mosfets as switches, which can. When v in is at logic low, q 2 is in forward active mode, and q 1 is off. Find the logical swing, noise margins and noise immunities for the mecl i circuit above.
An926 radiation design considerations using cmos logic rev. Introduction a logic family of monolithic digital integrated circuit devices is a group of electronic logic gates constructed using one of several different designs, and with compatible logic. The same techniques, however, can be applied to other types of ecl. Note that both transistors are enhancementmode mosfets. Combinational logic gates in cmos purdue university. Click the input switches or type the a,b and c,d bindkeys to control the two gates. Matched complementary pairs of mosfet transistors are packaged in the cd4007 chip. When interfacing 5 v cmos logic to ttl, a simple direct connection can be used. Integration levels gate transistor ratio is roughly 110 ssi gates chip msi gates chip. Lab 1 part 2 identify the 7400 series ttl gates and look up their data sheets.
When 5v supply is given to ttl and cmos ics, logic levels of ttl and cmos are different. Their gates are connected together to form the input, and their drains are connected together to form the output. Cmos technology introduction classification of silicon technology silicon ic technologies bipolar bipolarcmos mos junction isolated dielectric isolated oxide isolated cmos pmos aluminum gate nmos aluminum gate silicon gate aluminum gate silicon gate silicongermanium silicon 03121101 ece 4420 cmos technology 121103 page 2. An926 radiation design considerations using cmos logic. If either one of them is high 700 mv, then the or output is high, and the nor output is low. Cmos logic gates free download as powerpoint presentation. The ternary gates are implemented using recharge logic which can be exploited in binary and multiplevalued. The basic idea of currentmode logic is illustrated by the inverterbuffer circuit in figure. The third part of the ecl gate circuit is composed of the. In turn, the pun can only be conducting if one or more of the. Emittercoupled logic ecl based on bjt, but removes problems of delay time by preventing.
Digital ic families dtl ttl ecl mos cmos pdf each ic family has its own characteristics, limitations and advantages. The cmos driver must have a strong enough pull down to sink iil when the input to the ttl gate is low 0. Logical effort cmos vlsi design slide 27 gate sizes qhow wide should the gates be for least delay. Cmos static nand gate n second switching condition. Cmos gates are all based on the fundamental inverter circuit shown to the left. Transistors q 1 and q 2 are both arranged in the same manner that weve seen for transistor q 1 in all the other ttl circuits. Memory music, improve memory and concentration, binaural beats focus music duration. What is the typical range of supply voltages for a true ttl gate, and why cant this type of logic gate operate from a wider range of voltages as cmos gates can. Emittercoupled logic the key to reducing propagation delay in a bipolar logic family is to prevent a gate s transistors from saturating. As nand gates have pmosfets in parallel with nmosfets in series, both leakage current of the nchannel and increased threshold voltage of the pchannels are minimized. Cmos technology and logic gates mit opencourseware. 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. In this paper we present fault tolerant cmos logic using redundancy and ternary signals.
There have been many improvements in logical families such as ttl and cmos. Describe in your lab report each of their functions. Figure1 depicts ttl to cmos interfacing and cmos to ttl interfacing circuits. The applications discussed here include those where these devices are used to provide a specific function in a larger digital circuit. The circuit output should follow the same pattern as in the truth table for different input combinations. Consult a datasheet for the quad nand gate numbered 4011. Difference between ttl cmos ecl ttl vs cmos vs ecl. At vb vm, only m4 is conducting current only half the current. Cmos static nand gate university of california, berkeley. On semiconductor ecl logic gates are available at mouser electronics. This is a noror gate using emittercoupled logic, a highspeed type of logic using transistors. Now lets understand how this circuit will behave like a nand gate. Va vdd and vb switches from 0 to vdd at vb vm, the current through m1 and m2 is higher than when va vb since the gate voltage on m1 is now vdd and its vds1 must be smaller vgs2 is larger. The storage time is eliminated as the transistors are used in difference amplifier mode and are never driven into saturation.
To give concreteness to our study of ecl, in the following we shall consider the popular ecl 10k in some detail. As v a and v b both are low, both the pmos will be on and both the nmos will be off. Before proceeding to further sections, turn off the power and remove all wires and the potentiometer from the basic unit so you may make a fresh start on section 2. 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 value of the boolean function, implemented by the circuit. Cmos logic gates cmos field effect transistor free 30. The cmos nonthreshold logic ntl is derived from its bipolar. Boolean algebra, algebraic laws, minimization and minterms, applied to previous map, rs characteristics, d flipflop, cmos logic elements, cmos tristate buffers cmos tristate buffers, logic design, quinemcclusky, clocked dflip flop characteristics. Cmos circuits do not draw as much power as ttl circuits while at rest. Properties of dual static complex cmos gates i railtorail excursion. Is the fastest logic family and has the lowest propagation delay. Gates with a fanin greater than 4 should be avoided. Cmos circuit, what voltage levels should test points tp1 and tp2 be adjusted to, in order for the probe to properly indicate high and low cmos logic states. Introduction a logic family of monolithic digital integrated circuit devices is a group of electronic logic gates constructed using one of several different designs, and with compatible logic levels and power supply characteristics within a family.
The major ecl disadvantage is the very high power consumption. For practice or experiment using logic gate you can use logic gate made of switch, diode, relay and so on. The ecl emitter coupled logic families, originated in the late 1950s and. Keywords cmos, delay, nand, nor, power, powerdelay product, scaling. Lets examine the following ttl circuit and analyze its operation.
The students intent was to build a logic circuit that energized the led when the pushbutton switch was unactuated, and deenergized the led when the switch was pressed. Overview integration, moores law early families dl, rtl ttl evolution of ttl family ecl cmos family and its evolution overview 2. Ttl stands for transistor transistor logic, cmos stands for complementary metal oxide semiconductor and ecl stands for emitter coupled logic. The dip circuit is a hex inverter it contains six inverter or not logic gates, but only one of these gates is being used in this circuit. Effectively, these symbols represent the fact that we are now considering mosfets as switches, which can be placed either in an open state or a conducting state. Lower current draw requires less power supply distribution, therefore causing a simpler and cheaper design. This time the admin will explain the types of logic gate ic along with the schematics that can be used for practice. As a result, there are very definite limits on the. Ttl chips, even simple ics with the same types of gates as cmos, could not be. When vinvout, the nmos has vdg0, which means transistor is in the saturation region, since vdsvgsvtnveff is where saturation occurs onset of pinchoff. What are the advantages and disadvantages of ecl over cmos. If the pun is conducting, then the output will be high. Inputs 1 and 2 can be just wires connected as shown. Also show their logic symbol, use the function in an equation and show the truth table for one gate in each of the integrated circuits.
Applications of logic gates cmos logic gate free 30day. Cmos logic gates elementary logic gates are even more easily built from cmos. Twolevel gate andnand in ecl logic, or gates are preferred over and gates, and and gates are actually built from or gates. This page compares ttl vs cmos vs ecl logic families and mentions difference between ttl and cmos and ecl based on various parameters such as fanout,power consumption,noise immunity etc. Skewed gates skewed gates favor one edge over another ex. Zipper cmos m p m e v dd pdn in 1 in 2 in 3 m e m p v dd pun in 4 out1 out2 only 1 0 transitions.
Pdf analysis and optimization of seriesgated cml and ecl high. The above drawn circuit is a 2input cmos nand gate. A voltage transfer curve is a graph of the input voltage to a gate versus its output voltage. For this course, we need to study only ttl and cmos mostly ttl. Ttl nor and or gates logic gates electronics textbook. Thus, we must find a boolean expression for the uncomplemented output y. Within each family, several subfamilies of logic types are available, with different rating for speed, power consumption.
In the 70s ecl was the fastest logic family around, by far. Rather than functioning as amplifiers, q 1 and q 2 are both being used as twodiode steering networks. Explain why the allowable power supply voltage range for a true ttl not highspeed cmos logic gate is so narrow. This applet demonstrates the static twoinput nand and and gates in cmos technology.
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