OverviewBackground1. Diode Logic Gates2. TTL Logic Gates3. Exclusive ORPhysics 375, Laboratory 9Digital LogicOverviewThe purpose of these experiments is to investigate the properties of digital logic gates and the useof light-emitting diodes (LEDs) in digital circuits.BackgroundDigital logic is a type of electronics where the inputs and outputs have only two voltage values.These values are called 1 or TRUE and 0 or FALSE. The actual voltages depend on the particulartype of electronics used. We will use +5 V for TRUE and 0 V for FALSE. Tables comparing out-put voltages for a set of input voltages are called “truth tables”, and since there are generally afinite number of possible inputs, the table is usually shown with every possible combination ofinputs.Because digital logic involve only two states it is often easier to measure a logic level with a twostate measuring device than a voltmeter. The light-emitting diode (LED) works well for this sinceit can have two outpout states: ON and OFF.Digital electronics are commonly made into integrated circuits. We will use integrated circuitsfeaturing TTL-logic levels. The most common TTL logic gates are in the 7400 series. Thepinouts for the 74LS00 NAND has four gates inside and is shown below.To use any of the gates in the chip, it must be attached to both power (+5 V) and ground.+5 V123411121314VΑVBVout5671098GNDPHYS375Lab9,p.21. Diode Logic GatesUse two 1N914 diodes to make the circuit in figure 2.Figure 2: Diode AND-gate and LED logic probeMake a truth table for all four combinations of switch settings, recording the voltage levels with aDMM for VA, VB,andVout. Measure the logic levels with an LED logic probe, where the light onis 1 and the light off is 0, and make a truth table. How does Voutchange when the logic probe isattached? Use the results of part 1 to determine the most LED probes that could be run in parallelon Vout.+5 VVoutVB1kΩVAVin330 ΩPHYS375Lab9,p.32. TTL Logic GatesUse a 74LS00 NAND gate to make the circuit in figure 3 (don’t forget +5 V and ground).Figure 3: TTL NAND GateMake a truth table for all four combinations of switch settings, recording the voltage levels with aDMM for VA, VB,andVout, and measure the logic levels with an LED logic probe. How does Voutchange when the logic probe is attached? Switch both inputs to ground and place a 1 MΩ resistorto ground. Measure Voutwith the DMM and calculate Iout. Repeat the measurement for resistorsof 10 kΩ ,1kΩ, 470 Ω, 220 Ω , and 100 Ω.PlotIoutvs. Vout.3. Exclusive ORConstruct an exclusive-OR circuit from 5 NAND gates (2 74LS00s) as in figure 4.Figure 4: Exclusive ORUse the LED logic probe to measure the truth table for the exclusive OR.+5 VVoutVB1kΩVA+5