Linked Questions

7
votes
3answers
2k views

Why do TTL integrated circuits have such complicated schematics for logic gates with so many transistors as opposed to RTL?

I'm in the process of building a 4 bit computer out of discrete NPN BJTs and resistors. I'm using RTL, and I've made flip flops, full adders, and demultiplexers, and everything is working fine so far. ...
9
votes
2answers
8k views

How to combine multiple transistor logic gates without gigantic voltage-drop?

In follow-up to my previous question: Resistor values in transistor logic gates I've breadboarded all common types of transistor logic gates: XNOR, ...
3
votes
2answers
4k views

Building a full adder with NPN BJT transistors

So I'm trying to wire up a full adder just with NPN BJT transistors (I know there is a 74XX283 4-bit binary full adder, but I want to do it just with transistors if possible for my own learning). The ...
1
vote
5answers
1k views

Purpose of resistors in a NAND gate

I'm trying to build some logic gates out of transistors to eventually be able to make a full adder circuit. I've tried building a NAND gate multiple times but I can't seem to be able to get it right. ...
4
votes
3answers
585 views

How many transistors are there in a logic gate?

How many transistors are there in a logic gate? If anybody asks me, I tell them: A NOT gate is 1 transistor. A NAND gate is 1 transistor per input. A NOR gate is 1 transistor per input. An AND gate ...
2
votes
3answers
355 views

NAND with LED not working

ive been trying to create this small circuit but its not working. The truth table should be that of a NAND gate, but instead i get this: A|B|Q 0 0 1 1 0 1 0 1 0 1 1 0 I've put up the circuit in ...
2
votes
1answer
623 views

Choosing resistors for RTL gates

I'm interested in building a really, really simple computer I've been designing using resistor transistor logic gates like these: (when I can get away with it) (when all else fails!) I'll be using ...
-1
votes
2answers
349 views

What characteristics of a transistor to use for an 8 bit transistor computer

I recently purchased the book 'Code' which, for those who don't know, is an insight into how computers work on the hardware level - going down to basic components and how various parts of a computer ...
2
votes
1answer
122 views

Finding the broken cicuit in an Xor Gate

I am new to this particular stack site but I feel that this is the most appropriate place to ask my question. -Background- I've been following an online web course called Nand2Tetris that takes you ...
-1
votes
2answers
208 views

Trouble making a XOR gate with NAND gates

I'm trying to implement a XOR gate using NAND gates but I'm getting a short circuit in the part circled in the diagram. If anyone could help me fix this I'd greatly appreciate it. I made changes as ...
-1
votes
2answers
55 views

trying to figure out the differences between the six transistors provided by the schematic tool [closed]

My background consists of a BS in Computer Science and an MS in Computer Science and Engineering, both from the University of Washington. My MS consisted mostly in the very high level design of a ...
1
vote
2answers
56 views

Spike in RTL Inverter

I do not understand the cause of this spike which can be observed in an RTL inverter (but also in a CMOS inverter). In the following image it is the peak at 10 mS (I have considered as input a signal ...
0
votes
1answer
55 views

What are the resistors for in bipolar transistor based NOR gate?

In general I think I understand how this NOR gate works. What I don't understand is, why (in a very general view) there is a need for the resistors in this circuit. Especially the 4.7k Ohm one. I ...
0
votes
0answers
80 views

Help with a Full Adder setup

I've had a look around at all the various different ways to build a Full Adder and decided to have a crack at it myself. I looked at what it consisted of (2 XOR gates and a few AND gates) and built a ...
0
votes
0answers
51 views

Dimensioning a “NOT” gate with a bipolar NPN transistor

With the schematic below I am to determine a "NOT" gate the value of Rb to which the circuit acts as such, knowing that the voltages given for the logic levels are: $$0\to V\in[-0.3,0.9]$$ $$1\to V\in[...