Digital Electronics: Logic Gates - Integrated Circuits Part 1
in this experiment we're going to look at
circuitsand we're going to build some experiments from the course notes and implement them on our bread boards we're going to first look at the the chips themselves this is the type of chip that we're going to use the type that you're packaging we're going to use it's a it's the dip packaged and chip which is means plastic jewel line and pin package and the pins are space of three tenths of an inch a
partand you can see that your little circle here at the very top - indicates that that's pin one so there's a little notch at the very top of that chip and there's a circle Darrington indicates that this pin here is pin one so that we know how to identify with you're very careful that we order the dip package the dip package chips and we're working on our experiments disowning when you're doing your projects later on and there are other packaging types available this is this is an SOS e which is a small airplane too great a circuit and you can see it's a considerably smaller scale the inside of the chip might be exactly the same and might do exactly the same function so just the plastic packaging on the pin land and so on is what's different in this format again it's got a circle to indicate that pin one but you can see it's considerably smaller than the attended dip package chip it is possible that the chip that we don't that we want to use is only...
available in a dip package in it and in which case we can use a board like this it's a it's a converter board it allows us to it takes basically it takes in we can use these type of legs to convert into a yarn to allow us to plug it into our breadboard and on both sides of the board you see this design is this sign is point eight dot pitch on the other side is 0.6 and so in there in the point six this is a point six millimeters so you can see that we've lined up the line up the chip against the the channels and push the starter on today on to the
particular pins and then we would then be able to use these pins here in a more accessible way on our breadboard it is possible that certain types of chips that we need to use are only available in SOI c form and that means of in deflection format which means that we we would have to use a converter board like this okay so we're going to use we're going to use the dip format for our to dip packaging for our experiments so each each chip has an identifying number and here we can see that this one is the mm7 for safe safety 0h n the letters all mean something the AMM in this case refers to the manufacturer which is Fairchild Semiconductor it could also be letters like SN which would refer to Texas Instruments for example the 7/4 is the way that you know I suppose this is the gist did is to give away in terms of finding the number that makes sense on your chip to 7/4 and you skipped the letters in between seven four...
zero eight refers to the
particular type of chip this is a quad 2-input and gate so there's four to input on
particular chip the end at the end refers to the packaging type so we know that this is a dip packaging type so the N refers to different the dual inline package entitles and finally we have the HC t in the middle which refers to the the
logicfamily that the chip belongs to in this
particular case it's a high-speed CMOS with TTL
logiclevels so that this is the
particular type of of chip that we're going to be using for our experiments the first thing we need to do is we need to connect up the power to the chip so I've set up the rails so that we we have easy access and this
particular chip pin saddle has to be connected to ground and pin 14 has to be connected to VCC so here we're going to connect pin 14 to VCC and pin seven to ground stewardship is
partI haven't connected to supply yes percent the chip is
partand then we have now we have found our input on pins one two and three again we can tell her our first pin by the circle that's just visible there on the top of the chip we have pin one to our inputs and pin three as our output so we need some way of seeing our output so we're going to use an LED for this so I'm just going to use an LED on pin tree connect the LED well this is a piece of wire I'm gonna bring the LED over here and I'll just use a small resistor tied to ground that's...
before and then we just bridge that again remember in the longer leg is the positive is connected to pin tree and the shorter leg is connected to ground that's right to ground shoots a little resistor so now we have our circuit and we could test this and we can say well let's connect both of our inputs to be high and in this
particular case when we can we turn on the power you should see very quickly our LED should light pins one and two okay both to grab yeah both - sorry book to VCC to five volts when we when we we turn on our power supply now you'll see that the LED lights I'm just going to leave the power supply lish am I going to disconnect one of my inputs and connect it to ground and there is scene if now that is connected to ground the LED is off if I do it on the same with the other pins it will have the same effect you know from the light the truth table for a a NAND gate that both inputs have to be high for the LE it's okay again set Bowden puts me high then we can light or LED like this now what we're going to do is we're gonna say well moving these wires around it's a little bit awkward so let's connect in two switches so I'm just going to tie off the power and connecting two switches so I'm going to use these push-button switches and just make sure you have them in the correct orientation and we're going to connect these across I'm going to connect the first one so that it's touching pin it sits in the same...
role as pin 1 so that means that I'm on you're gonna have to connect to the other side of it of the switch just make sure they do a fiddly they might come out and I'm gonna put the other switch and right beside okay so we have two switches don't push them in well into the boards and these buttons are going to provide my inputs and we should see that when our circuit work my circuit is connected that we get a high only the LED lights we could have high only when both buttons are pressed at the same time together so we need to connect up to say well well let's say well let's connect the behind to this to this side of this pin make sure you go to the right thanks to the other side let's connect off our goes in at the other side of your switch let's connect that to the second input and the second switch is already connected into pin 1 and we just need to connect the other side with into our fire she was going to up should reach now we turn on your circuit you're gonna see something unusual happen it doesn't work and if we press the buttons and we receive it well the LED nearly always stays on so it's having no effect but you should see that the LED flickers on and off as it goes so see that's not very stable now the reason for this is because well let you think about for a minute what the reason for this is why why is it unstable so why does it seem to flick between on and off as I'm pressing the buttons even though with no...
input and it should ensure that the moment be off you think about that