Questions tagged [resistor-transistor-logic]

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7
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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. ...
0
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1answer
79 views

Linear technology power supply, question about a transistors

On page 12 of this journal there is a power supply design by LT. On page 14 there is a complete schematic. I understand everything but these two parts: There is a negative supply of -5V connected ...
0
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2answers
129 views

Why is D2 switched off and T4 not in saturation mode in 7408 TTL Gate as shown below?

In the circuit, when both the inputs are high at 5V, than why is D2 switched off? Will it not draw voltage from Vcc? Also, when one of the input is low, why is T4 not running in saturation mode? Will ...
0
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2answers
88 views

Using transistor output as a logic input

I'm trying to use the output of the following transistor circuit as an input for XOR gate. It doesn't seem to work, I'm out of ideas. Any help would be appreciated.
2
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4answers
292 views

Indicating 3V3 and 5V with 2 LEDs

I am building 3V3/5V source for my breadboard. The actual voltage will be selectable by the switch. I would like indication, which voltage is actually selected by lighting green LED for 5V and yellow ...
0
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3answers
4k views

What are the limitations of using a LDR sensor?

I have to explain limitations for a photoresistor/LDR . I've read the book, and searched online but find nothing. Can I get help with this ? Are things that the sensor can NOT do, which other tools ...
1
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2answers
114 views

LED in NOT gate confusion: LED voltage drop vs transistor voltage drop

I saw a schematic for building a NOT gate, it worked, but there's something I don't understand. Here is a pic of what I did (sorry about my finger hiding the push button) If I push the button, the ...
3
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1answer
161 views

Electron flow with pulling resistors

I'm very confused on the idea of pulling resistors. I get that they set the default voltage to a value so that you don't get a floating high or low value, but I don't get the application in TTL. So ...
0
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1answer
410 views

Error Logic Gates [duplicate]

I connect this 5 transistor and,or,nor,nand,inverter respectively into to switches to operate.. I also add Exor and Exnor.. the Exor I made consists of 4 Nand gates based on the nand diagram stated on ...
1
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3answers
627 views

LED with a transistor on each side

I'm trying to make a circuit with a transistor on each side of an LED so it only lights up when both transistors are activated. The transistors need to be on either side of the LED because the LED ...
0
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2answers
4k views

Using 25 IR LEDs with Raspberry Pi and Transistor

Using a Raspberry Pi and 5V I want to use 25 IR LEDs (5mm LED, 940nm wavelength, 20 degree beam width, 100 mA continuous, 1000 mA pulse, Approx 1.6V forward voltage; http://www.exp-tech.de/super-...
-1
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2answers
251 views

The resistor's power consumption of 1 ohm in watts

I ran into a old-midterm exam question that calculate the one-ohm resistor's power consumption in the following diagram in watts? I need some solution or hints. I try to solve it but I think the ...
1
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3answers
722 views

What is the best transistor for a large RTL (resistor transistor logic) project?

I've been reading up on older computers like the PDP-1 and TX-0. I'm fascinated with them and love the idea of making a CPU of my own using discrete resistors and transistors. Keep in mind, this is ...
-5
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2answers
340 views

Car Gear Indicator [closed]

I'm new in here and I'm very new to electronics and have a very little knowledge about it. I'm trying to do a project in where I have a car with manual gears 1,2,3 & 4. Each will be represented by ...
5
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3answers
2k views

How do I invert a signal without deforming it, and without using a logic gate?

I have an IC which outputs pulses over an open collector pin. I need both these pulses and their inverses in my circuit. I want to do the inversion by using as few as possible transistors and without ...
1
vote
1answer
307 views

NAND gate from BJTs: interfacing +/- 12v op-amp and 5v logic: destroy BJT with excessive Vebo?

I want to switch on a relay when both a 5v logic input is high and a (LM741 used as a) comparator is around +10v, and the circuit I planned to use is below. The problem I see with the circuit is when ...
1
vote
3answers
8k views

Why do optocouplers require a resistor at the collector?

In this circuit, if the resistor in the collector R1 is 0 Ohms, the circuit doesn't work. That is, the output will be 12V DC signal as it is from the battery. And if R1 is non-zero, then the circuit ...
9
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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, ...
6
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2answers
12k views

Resistor values in transistor logic gates

I breadboarded some AND, OR, NAND and NOR logic gates (...
4
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1answer
24k views

XOR gate; transistor level design [duplicate]

What would a transistor level design of an XOR gate look like?
3
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2answers
4k views

What values / components do I need in this flip-flop circuit?

I need a circuit to make a relay toggle when pushing a push button. I found this circuit here: It looks good for me - please tell me if it won't work. I intend to work with a push button to Vcc and ...