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Ttl transistor diagram and gate9/2/2023 ![]() ![]() The question rather than the question itself. It takes a little getting used to,īut in many cases a more optimal solution can be found by asking the opposite of ![]() NOT, NAND, and NOR rather than AND and OR. In digital electronics it is usually much more optimal to think in terms of Its output, so a NAND is a little easier to implement. Of course we could create an AND gate, but then we would have to invert The design now as a block and create other gates. So a single transistor can be used as an inverter. We at least have a TTL inverter that given solid inputs outputs TTL To see if we match the tolerance on those constraints, but that’s not Of course, we haven’t tested against the Vil, Vih values It’s almost perfect! And in reality, the output low will Table 3.1 Logic/Response Table for the "Model" TTL Inverter Lists the inputs and outputs, so you can confirm everything at once and assure Get a 0.6V output roughly (logic 0), and thus we have an inverter. Therefore, when we apply a signal of 5V (logic 1), we (5V-4.4V)=0.6V, which is above the requirement of 0.2V worst case for theĬollector above ground. Thus, the voltage at the collector VC and the output Z (Vout) is However, this is only tentative it may be less if this current violates one We know that IC = hFE*IB roughly, and assuming an hFE of 100, we get an IC Voltage drop over Rin divided by the resistance of Rin: So the base-emitter junction wants to have a 0.6V drop across it therefore, theĪnd since VE is at ground, VB = 0.6V. When we do this we turn ON the transistor and it starts conducting. Let’s apply a 5V (logic 1) to the base at X (Vin) Thus, an input of 0V (logic 0) outputs a 5V (logic 1). Than a very small leakage current), therefore the output Z (Vout) will output OFF in this case, there is no base current and thus no collector current (other If we apply a 0V to the base at input X (Vin) then the transistor is Signal then you can usually derive everything from there, so we will start withģ.67 depicts one possible design. The inverter is the basis on 99% of all digital logic if you can invert a "TTL" gates with those constraints or at least close. With that in mind, we need to design our model The digital systems use +5V and that a high or "1" is +5 and a low or What a TTL gate will detect as a low and high as an input. Two things: what a TTL gate guarantees as low and high when it is an output, and These seems a little weird, but the bottom line is that we need to consider Levels for various switching logic families. TTL gate is guaranteed to output a high at. Voltage a TTL gate will give when output a low. VCC/GND-These are the "rails" of the power.Referring to the TTL switching standard there are a number of demarcations on Interested in the TTL family for now, since it’s easiest to model. Levels for a number of different logic families (courtesy of TI). What is the voltage level representation of a logic "1"?ģ.66 you will see a graph that shows the logic.What is the voltage level representation for a logic.Implementation of TTL since we are just trying to make something that is (transistor transistor logic), which refers to both a method of implementationĪnd a set of voltages and currents. To loosely model our gates after the most popular logic system in the world, TTL Of conventions that is, what means what in relation to voltages? We are going The first thing we need to agree on for our little model experiment is a set This way you can see the transition from analog toĭigital better, but still realize that under all the digital electronics areĪlways analog components-always. Logic gates from transistors and resistors that implement these logic functions Through the same thought process the IC designers did and build some simple To do this of course the way we will do this in the next chapter is with ICs So the question is, how to implement this in hardware? There are lots of ways Only then can we map our computer code directly to hardware and make assignments With this in mind, if we are dealing with Boolean values Of course the "logical" NOT, AND, and OR are somewhat different andĭeal with entire numbers however, at the bit level, logical operations andīitwise are identical. This assigns z the bitwise OR of x and y. This assigns z the bitwise AND of x and y. ![]() This assigns x the bit inverted value of y. You may have no idea what a digital logic gate is, but briefly, a logic gate isĪ hardware implementation of the standard logic functions you use when Learn More Buy 3.10 Framework for TTL/CMOS Logicīefore we enter the digital realm and leave the world of analog electronicsīehind (for the most part), I thought it would be fun and very relevant to showĮxamples of how transistors are used to create digital logic gates. Black Art of Video Game Console Design, The ![]()
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