Questions tagged [ttl]

Transistor Transistor Logic. Logic circuits built from bipolar transistors and resistors.

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Why do TTL pulse generators generate an asymmetrical square wave (unlike CMOS)?

I've read that the asymmetrical (about 1/3 mark-to-space) output waveform is due to input gate characteristics of a TTL inverter, but I want to know more about which characteristics of the TTL input ...
2
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1answer
121 views

How to replace TTL PROMs in a design operating at 20MHz

I am attempting to come up with a reasonable way of implementing a design that was intended for cheap computer applications in the 1980s and which was originally designed to use a pair of TTL PROMs (a ...
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4answers
3k views

Buffering a Digital Microcontroller Signal for Connecting to an Optocoupler

I frequently work on projects in which I use optocouplers for isolating digital +5VDC control signals (for example, from a microcontroller) from the rest of the circuit. However, since these work by ...
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3answers
930 views

Introduction dates of different 74xx or 40xx chips?

The 74xx family debuted in 1964 with the 7400 chip, and the 4000 family debuted in 1968, but not all chips with 74xx or 40xx part numbers debuted anywhere near that time. If one wanted to invent a ...
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2answers
222 views

7400 chip register with common in/out pins

First of all, I don't know if this kind of question is allowed here, so sorry if it isn't. I am looking for a 7400 series register which has common in and out pins (like for the RAM ou EEPROM: ) with ...
7
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1answer
11k views

How to convert a digital signal from 24V to 5V

I have an industrial automaton that gives me a digital signal (24V or 0V) on its outputs and I want this signal to control an integrated circuit, but the integrated circuit only takes a TTL signal in ...
7
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1answer
10k views

TTL voltage shift from 5 to 3.3 Volts “UART”

I want to make serial communication with a device which works on 0-5 Volt TTL level. But my serial chip uses 3.3 Volt logic. (this is an UART communication) I know that I need a step down at least ...
13
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1answer
4k views

How is this circuit for level converting (5V<>3.3V) working?

Does anybody know, how is this circuit exactly working? It is level converter between 5V and 3.3V logic and it is bi-directional. I have some theory, but I am not sure with it (I never worked with ...
1
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1answer
374 views

TTL input ouput logic

I came up with voltage levels of TTL logic. I know that logic high is 2-5V for input and 2.5-5V for output. But why there is an additional 0.5V rise in the logic HIGH of output. Is there any ...
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2answers
389 views

VHDL Sending Data from FPGA to TTL

I asked same question in stackoverflow but didn't get any good answer. I'm newbie in FPGAs and VHDL. This time, I m trying to send Data from FPGA to TTL. I' m using GPIO pins for TX and GND and Data ...
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3answers
813 views

Sensor with TTL digital output

I'm working with a position sensor (Correvit Aqua L-350 by the manufacturer Corrsys-Datron) that gives me 0 to 5 V pulses everytime a distance (which I can choose on its software) is swept. User ...
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1answer
41 views

Changing from 8 channel to 16 channel. Does change in voltage input affect upgrade?

I am going from a Numato 8 channel GPIO to a Numato 16 channel GPIO. The 8 channel I/O pins support 5V TTL signals but the 16 channel I/O pins support 3.3V TTL signals. If the input to the I/O of the ...
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1answer
361 views

SN7404 inverter strange input low current

When I connect the SN7404 pin 1 to ground and measure the current, the current is nearly zero (5uA at most). I would expect the input low current (I_{IL}) is usually around 1mA magnitude. I tested to ...
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1answer
408 views

Converting to a TTL signal?

I am working on a project that needs to convert a high input/output voltage into a TTL signal. The box I am working with has a parallel port output that was supposed to send out a TTL signal when a ...
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1answer
193 views

convert TTL/CMOS output signals to 0V and 5V [duplicate]

Is there an easy way to convert TTL/CMOS output signals to 0 and 5V? For example, if an ic outputs 0.1V as "0", I'd like to convert it to 0V and if it outputs something like 3.9V as "1", I'd like to ...
0
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1answer
437 views

voltage drop across collector and emitter when using transistor as a switch

I am trying to send TTL pulse from Arduino to 8 raspberry pi simultaneously. For this, I am using npn transistor as a switch. Below is the circuit for same: Note: MB102 is a power supply that takes ...
1
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1answer
686 views

How can I boost/limit a signal to TTL levels?

I am researching a data acquisition system to measure the amplitude and frequency of a 4,100Hz 5v-25v AC square wave signal. Actually this is version 2 for me, in the previous version I analyzed the ...
4
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2answers
2k views

How to convert sine wave from an oscillator to TTL signal for microcontroller?

I tried to measure inductance by using a colpitts oscillator to generate sine wave. It works. I need to convert the sine wave to 5V square wave to feed to a microprocessor. The sine wave is coupled ...
1
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1answer
66 views

Which area of physics deals with principle of work of BJTs, diodes and other semiconductor elements and which book do you suggest covering this? [closed]

Which area of physics deals with principle of work of BJTs, diodes,...? I'm familiar with equations that describe operation of these elements but I have no idea how they work "internally". I started ...
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1answer
1k views

Fan-out of TTL inverter

Here is my attempt to find fan-out for TTL inverter circuit. As you can see, I did analysis for high input (low output) and used condition for saturation of output transistor Q3 to find max. number ...
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2answers
2k views

Which logic families interpret a floating input as a definite value?

From what I remember, from decades ago, 1980's 5v TTL chips would see a floating input as a zero (because they switched on current, rather than voltage). Update: it seems they were interpreted as ...
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0answers
217 views

CP2108 with level converter txb0108 - UART communication TTL and LVTTL

My project uses four different modems (one 3v3 LVTTL(?) and three 5v TTL) for AT communication. Each modem has a UART interface (TTL compatible). For my application, i chose the CP2108 to ...
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2answers
177 views

how to deal with input voltage that is between device logic high and logic low voltage

TTL logic level says that if input voltage is above 2V it is high and if below 0.8V it is low. what if the input voltage is between 0.8V to 2V, how does one deal with such voltage range to convert the ...
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2answers
644 views

How to “hold” TTL pulse

How would I produce a pulse like this image? This is to power and actuate a solenoid valve. I'm using a 3D printer Arduino board to do this. This is what I have so far. The if code_seen() passes a ...
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2answers
101 views

What is the difference between a 74*374 and a 74*377

What is the exact difference between a 74*374 and a 74*377? The first is classified as an octal edge triggered d-type flipflop while the latter is an 8-bit register. I don't understand the difference ...
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2answers
311 views

current limiting resistors

I notice that in Ben Eaters project for the 74 series logic chip computer, which my son and I are building, sometimes he uses current limiting resistors on LED's on the pins of some chips, and on ...
2
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1answer
405 views

L293D and PWM on enable pin: TTL voltage drops to 4 Volts

I'm building a simple motor shield for Arduino based on the L293D bridge driver. I'm doing some tests on a breadboard everything is fine as long as I drive the motor at full throttle with DC inputs (...
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0answers
787 views

4 bit binary full adders, bcd and seven segment displays

I'm having fun with some 74LS283[1] 4 bit binary adders but I am having trouble working out how I should convert the output to a decimal which could be used to drive two 7 segement displays which are ...
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4answers
403 views

Failure mode of TTL device

A question came up about common failure mode of a transistor. Searching past posts I actually found varying answers, either open or short. Maybe it depends on the application, and I'm missing ...
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2answers
219 views

How do I find resistor values for an LSTTL to ECL interface?

LSTTL is a 74LS10 three input NAND gate ECL levels are -0.75 volts and -1.55 volts Supply voltages are +5 volts and -5.2 volts I am really not sure how to proceed with this. I've tried setting the ...
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3answers
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What does a two overlapping circles symbol mean in an electrical schematic/diagram?

In the datasheet for a A3503 Hall Effect Sensor, I saw a circuit diagram labeled 'Functional Block Diagram', and it shows a symbol I have not seen before. It's shown here between 3 - Output and 2 - ...
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2answers
128 views

uart TTL problem

My Setup I have an Arduino Mega connected with my PCB and both boards exchange data using UART TTL @ 57600 baud rate. Both have their own separate power supplies (5 Volts each; Mega is powered via ...
0
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1answer
364 views

How can I raise a CMOS 1.8V output to 5V LVTTL input with a MOSFET?

simulate this circuit – Schematic created using CircuitLab I'm trying to drive a 5V LVTTL UART input on a ATMega32u4 with a 1.8V CMOS ouput on a Telit UL865. I'm using the NTE2987 enhancement ...
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4answers
3k views

Should I use CMOS vs. TTL?

Now, I know that this question has been asked so many times that it seems like I'm trolling, but I must point out that I couldn't find the right answer to this question anywhere. So yeah, CMOS and ...
3
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3answers
915 views

nuclear instrumentation module

This is my first time posting on this forum, so please bear with me. I'm trying to design a 'logic converter' to convert a signal from one logic standard to another, and vice-versa. The first logic ...
2
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2answers
253 views

Limitations of Arduino Voltage Pulse? (TTL)

I am new to this forum, and I have a question regard EE and Arduino based boards. Are Arduino based boards capable of producing pulses in the range of MICROseconds (usecs)? For example, I would like ...
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1answer
1k views

Externally Triggering a camera Using a TTL Signal [closed]

I am not an electrical/electronic engineer, so please bear with me. I have a monochromatic camera (www.qimaging.com/resources/pdfs/QICAM-12bitManual.pdf) which can be triggered (i.e. capture image) ...
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5answers
286 views

How to “shift” a logic LOW of 2,5 V to GND?

I'm trying to control a 24 V LED strip with a device that has its own control mechanism and PWM output. (The output PWM frequency is 1 kHz.) The device itself requires 5 V, and since it does not draw ...
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0answers
715 views

How to make a multi emitter BJT transistor? [duplicate]

Im trying to create the 74XX series IC's from scratch, using just transistors, resistors and diodes. I intend to chain them together and create some logic systems. Right now i'm trying to create a ...
0
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2answers
317 views

What is the Vout of 74154 demux and 7404 hex inverter?

I've read through the datasheet of 74154 and have seen that its Vout ranges from 0.5V to Vcc+0.5V. So if the Vcc is 5V, I am assuming I can get 5.5V max Vout in the output pins. However, a friend of ...
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1answer
878 views

Can I Hook a Raspberry Pi Zero to a Laptop Display Via HDMI to TTL and TTL to LVDS?

Dilemma: I have a project in which I am trying to use a Raspberry Pi Zero to display static content through a laptop screen. I am trying to make my unit as thin as possible and use as little power as ...
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2answers
200 views

Annoying problems getting started with logic circuits (SN74LS)

I'm trying to get started making logic circuits but I'm not making much progress even with the most basic. I have a SN7408 which is an AND gate however it doesn't matter what I put over the inputs (1A ...
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1answer
214 views

how many 7400 can the 74LS04 safely drive

how many 7400 can the 74LS04 safely drive ? 74LS04 Specs : I output low : 8 mA 7400 Specs : I input low : -1.6 mA PS : I know that the answer either 5 or 2. The only thing I am not sure is ...
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1answer
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TTL 7400 NAND gate circuit not functioning [closed]

I recently made a circuit using the ttl 7400 NAND gate IC. The concept is simple. There are two 4 bit inputs going into the 7400 IC. The 7400 IC does a 4 bit NAND operation on these bits, and outputs ...
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2answers
4k views

Should I connect unused STM32 pins to ground?

I'm designing some circuit using STM32L152RBT6 microcontroller. I'm using STM32L-DISCOVERY scheme as a reference of good STM32 practices. I've noticed that free pins of programmer's MCU aren't ...
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1answer
384 views

Convert ps/2 to usb using ttl to usb converter [closed]

I have an old keyboard that has ps/2 interface. I have a ttl(V G tx rx) to usb converter too. Can i use this converter to connecting my keyboard to USB port? What about RS232/RS485 to USB converter? ...
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3answers
539 views

Generate Short negative pulse from an open collector output?

Ive been teaching myself as I go so please forgive me for any errors. I need the output of an open collector output (goes to ground when active) to henerate a short negative pulse to reset the counter ...
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2answers
2k views

USB to TTL converter: why doesn't TX need a voltage selector?

I plan to flash new firmware for a Sonoff ESP8266-based switch. So I need a 3.3v USB to TTL for the programming. I see an inexpensive converter from China which has pinouts for 3.3v TX RX GND 5v ...
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1answer
397 views

S/PDIF to TTL converter

This is how S/PDIF to TTL converter usually looks like. I simulated poor quality smoothed out signal with a sine wave. Can comeone explain how it really works? Inverter with feedback resistor ...
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1answer
3k views

Creating a one-digit scoreboard using logic circuits

I'm creating a one-digit scoreboard on a breadboard. Naturally, I have a BCD to 7-segment decoder and a 7-segment display. But I don't know how to automatically increment the display. (It's for a game,...

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