Characteristics of 74 Series Logic Families - Lab Report Example

Lab Report, Engineering and Construction ID Number To Measure the Electrical Characteristics of 74 Series Logic Families Institution Name Date Abstract There many devices in the 7400 IC series, numbering to hundreds, which serve various purposes such as logic gates, digital flip-flops, counters, ALUs and bus transceivers. In the contemporary world of electronics, many electronic systems use the CMOS connected to the surface of many devices including computers and industrial systems. The initial part of the series, 7400 implies that a device carries four 2 - bit NAND gates, each using two input pins and one output pin. It has two more contacts, one to the ground (earth) another to a +5 V power supply. It is covered in a dual inline package, having fourteen pins. This package is made of ceramics or plastic to prevent short-circuiting of power. Table of Contents Page 1. Introduction 5 2. Theory 5 3. Experimental Method and Results 6 3.1. Typical Voltage and Current 7 3.1.1. Method 7 3.1.2. Results 7 3.2. Static Transfer Characteristic Curves 7 3.2.1. Method 7 3.2.2. Results 7 3.2.3. Comparison 11 3.3. Loading Effects 11 3.3.1. With 7404 11 3.3.2. Repeating with 74LS04 12 3.4. Noise Margins 13 3.4.1. Method 13 4. Discussion 14 5. Conclusion 15 List of Symbols Ω - Ohms μ - Micro 1. Introduction The purpose of this study is to explore the physical, functional and logical properties of logic circuit devices in the 7400 series, specifically, the 7404 inverter circuits. A typical Transistor to transistor logic for the device is shown in figure 1 below. Figure 1: TTL of the 7404 Inverter Device Series This study uses a practical laboratory experiment to test the characteristics of the devices. The laboratory exercise involves the investigation of the characteristics of the TTL logic devices and the CMOS logic family series (Millman 1979, p. 49). The expectations of the lab experiment are the measure of the voltage transfer properties and the power dissipation delay and power propagation delay for the TTL of 7404 inverters as well as CMOS (Eren 2003, p.14). The experiment is divided into four fundamental sections. The first section investigates the typical currents and power voltages. The second section measures the static transfer property curve. The third section is the investigation of the loading effects. The final section is the noise margins measurement. 2. Theory In theory, the power supplies V+ is represented with while the ground connection is V–, with an almost zero voltage. The greatest input voltage identified as the logic low input IL, produces a corresponding output being VOH (Lancaster 1975, p. 49). The greatest output voltage identified as the logic high input IH, produces a corresponding output being VOL. The noise margin is created by the allowance of safety between the output in one gate and the input of the next gate. The calculation of the low side noise margin is done using the equation 1 below: ------------------------------------------- [1] The calculation of the high side noise margin is done using the equation 2 below: --------------------------------------------- [2] According to Gray & Searle (1969, p. 87) the gap between Voltage VIL and VIH cannot be identified. It is therefore difficult to predict their outputs if the voltages are used in the logic gates. The calculation of the mean power dissipation is done by the average of the power dissipation between the 2 logic states (Marston 2013, p. 16). 3. Experimental Method and Results The requirement for these experiments include RS prototype Board Digital multimeters 0 to 30 Volts of DC Power IEEE equipment for demonstration of tests 390 Ohms Resistor 470 Ohms Potentiometer 74 series integrated Circuits 3.1. Experiment 1 Experiment 1 is an investigation of the Typical Voltage and Current. Method (i). The experiment began by selecting the 7404 inverter for testing, and connecting it to the power supply of +5V as shown in figure 2 below. Figure 2: Testing Circuit The next step is the adjustment of the potentiometer for low input voltage VIL (0.4V), and taking measurement of the high output voltage (VOH). The third stage is the adjustment of the potentiometer to produce a high level input voltage (VIH = 2.4V), and measuring the low level output VOL and the high level input of the current (IlH). The process is repeated with the logic gate 74LS04. 3.2. Experiment 2 Experiment 1 is an investigation of the Static Transfer Characteristic Curves. Method From the set up in figure 1, the experiment began by an adjustment to the potentiometer to provide an input voltage of between 0 and 5V, followed by measurement of the corresponding voltages. Results (i) Table 1: Results With 7404 From Lab Experiment Manufacturer’s Speficication Comparison with The Manufacturer’s Specification VOH 4.4V VOH 6.0V Less than Manufacturerd specification VOL 0.5V VOL 0.4V Higher than Manufacturerd specification IlH 1μA IlH 1μA Equal to the Manufacturerd specification Results (iv) Table 2: Results With 74LS04 From Lab Experiment Manufacturer’s Speficication Comparison with The Manufacturer’s Specification VOH 4.7V VOH 4.9V Less than Manufacturerd specification VOL 0.4V VOL 0.5V Less than Manufacturer’s Specification IlH 1μA IlH 1μA Equal to Manufacturerd specification Table 3: Output Voltage against Input Voltage VIL(V) VOH (V) VIH (V) VOL (V) 0 2.4 0 0.8 1 2.4 1 0.8 2 2.7 2 0.8 3 2.7 3 0.8 4 4.95 4 1.67 5 4.9 5 1.6 Results (ii) Figure 3: VOH vs VIL Figure 4: VOL vs VIH Table 4: Vin vs. Vout 7400 and 7404 Vin(V) 7400 Vout(V) VT 7404 0 3.997 4.17 1 0.58 0.48 2 0.306 0.206 3 0.302 0.206 4 0.371 0.281 5 0.45 0.15 Figure 5: Curve for 7400 series and 7404 TTL Gate Comparison The Two Curves move display similar results between 0 1nd 1 volts then the output for the 7400series inverter becomes slightly higher for the rest of the input voltages. The output is connected to +5 V with the external pull-up resistor to minimize the amount of current that is drawn from the power supply of +5V while the switch is closed (Seraphim & Feinberg 1981, p. 67 - 68). Because of that, the real amount of resistance does not become critical because real circuits utilize values in the range of kΩ to 10kΩ. 3.3. Experiment 3 Experiment 1 is an investigation of the Loading Effects. With 7404 The wiring was done according to the circuit in figure 6 below. Figure 6: Test for Loading Effect (i) Current pulled by 7404 IOL= 10.7mA (ii) Current IOH = Voltage / Resistance = 5 / 390 = 0.012821 Amps =1mA (iii). Fanout = IOL / IIL Fanout = 10.7 mA / 1mA Fan-out = 10.7 mA / 01mA = 10.7 (iv). Fanout = IOH / IIH Fan-out = 1mA / 1mA Fan-out = 1mA / 0.1mA = 1 The calculation for the Fan-out in (iii) is 10.7 while the fan-out in (iv) = 1. The corresponding manufacturer’s fan-out is 10 and 1 respectively. There is an error in the first fan-out, causing a difference of 10.700 – 10 = 0.7. The possible cause of error is inaccurate observation of the measurements while reading the inputs. Repeating with 74LS04 (v). Current pulled by 74LS04 IOL= 4mA Current IOH = Voltage / Resistance = 4.75 / 390 = 0.0121 Amps Current IOH = 1.2mA (vi). Fanout = IOL / IIL Fan-out = 4 mA / 1mA = 4 Manufacturers fan-out = 5 Difference = 4 – 2 =-1 (vii). Fanout = IOH / IIH Fanout = 1.2 / 0.1 = 12 Manufacturer’s fan-out = 10 Difference = 12 – 10 =2 There is an error causing the differences in fan-out (v) and (vi) of -1 and 2 respectively. The error is possibly caused by reading of wrong inputs. The number of 7407gates driven in 74LS04 gate = 10 / 1 = 10 (taking the ratio of fan out vii to iv). 3.4. Experiment 4 Experiment 1 is an investigation of the Noise Margins. Method The setup of the experiment is done as shown in figure 7 below Figure 7: Test of Noice Margins (i) VOL = 0.4V (ii) VIL = 1.5V Voice Level VL= VIL (max) – VOL (measured) VL = 1.5 – 0.4 = 1.1V (iii) . VOH measured = 4.5V VIL = 1.5V VNH = VOH (measured) – VIH (min) VHL = 4.5 – 1.5 = 3V Comparing with the result for VOH = 0.4 VNH = VOH (measured) – VIH (min) VHL = 0.4 – 1.5 = -0.9V In this, the experiment cannot operate since there is a negative voltage 4. Discussion 4.1. Results and Analysis The findings of the experiment were within the acceptable maximum and minimum boundaries stated by the manufacturer. For example, the current output in the loading effect for the 7404S series was 1μA. The manufacturer also presents this as the standard maximum current. The Input and output voltages for the 7400S devices were greater than the 7400LS series, an indicator that the 7400LS have greater fan-out measures than the 7400S series. The laboratory experiment was successful in the objective to measure the characteristics of the 74 series logic families (Westman 1968, p. 73). There was a very little gap between the experiment measurements and the specifications of the manufacturer. The lab exercise applied a different manufacturing method to integrate transistors and high value resistors for minimizing the consumption of power in the 74 Series. The 74LS family of semiconductor ICs has a slightly higher speed but lower in power dissipation compared to the original versions of the 74 IC families. As the 7404 series IC takes 8ns in power dissipation, th4 74LS04 takes a maximum of 4ns in power dissipation. In that regard, it is the most available and most applied variant of the 74 series. 4.2. Error Analysis The laboratory experiment was successful in the objective to measure the characteristics of the 74 series logic families (Westman 1968, p. 73). There was a very little gap between the experiment measurements and the specifications of the manufacturer. The lab exercise applied a different manufacturing method to integrate transistors and high value resistors for minimizing the consumption of power in the 74 Series. As it can be seen, some of the specifications found in this study differed from the manufacturer’s specifications and had varying measures of voltages and current for the same power supply of +5V. The properties of the two IC families shows 7404 to have an average higher input and output voltage, but the same amounts of input and output currents as shown in table 5 below. Table 5: Comparing properties of Manufactures and Lab Findings Parameter Manufacturer LAB Error VOH 4.9V 4.5V 0.4V VIH 3.5V 2.0V 1.5V VOL 0.5V 0.1V 0.4V VIL 1.5V 0.8V 0.7V IOH 0.4mA 4mA 0mA IH 1μA 1μA 0 IOL 0.4mA 4mA 3.6mA IIL 1 μA 1 μA 0 μA TP 8ns 4mA 4ns 5. Conclusion During the laboratory experiment, the lesson learnt was the properties of the TTL low and high input values needed to achieve the required operational mode. Additionally, the power dissipation behaviors were observed during the comparison between the 7400 devices and the 7400LS. It was clear that there is no compatibility between the 7400 and the 7400L with regards to power consumption. The 7400S are able to handle greater power than those of the 7400LS (Maini 2007, p. 67). The laboratory experiment also revealed the importance of fan out in controlling power utilization. References Eren H 2003, “Electronic Portable Instruments: Design and Applications”, CRC Press. Gray P E & Searle C L 1969, Electronic Principles Physics, Models, and Circuits (1st ed.), Wiley, p. 87. Lancaster D 1975, TTL Cookbook, Howard W. Sams and Co., Indianapolis. Maini A 2007, Digital Electronics: Principles, Devices and Applications. John Wiley & Sons. p. 68. Marston R M 2013, Modern TTL Circuits Manual. Elsevier. p. 16. Millman J 1979, Microelectronics Digital and Analog Circuits and Systems, McGraw-Hill Book Company, New York, p. 49. Seraphim D P & Feinberg I 1981, "Electronic Packaging Evolution in IBM", IBM Journal of Research and Development 25 (5): 67–68. Westman HP (ed) 1968, “Reference Data for Radio Engineers”, 5th Edition, Howard W. Sams & Co., Indianapolis. Read More