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Questions tagged [ttl]

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

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50 views

TTL “radio-button” using priority encoder and latch

I'm liking this site and I am not always using it to just throw a question but to develop ideas all the way. First time I did that was on StackOverflow I need JSZip and gzip for my web page, and JSZip ...
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43 views

Are there combo gates XOR followed by AND? (4-bit identity comparator)

Is there no 4 bit identity comparator in TTL or CMOS? It could fit into a DIP-12 package as all it would have is 4 XOR gates for selectable invesion and 1 4-way AND gate. OUT := (A1 xor B1) and (A2 ...
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465 views

Using HC/HCT, AHC/AHCT series logic

I am builing a circuit, and i need to connect a few different IC's (obiosly). My circuit is based on 5V TTL logic and i found a part that is made only in AHC/AHCT variant. So let's take it from the ...
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187 views

Is this circuit from a textbook wrong?

(This is not a homework question.) While reading "Digital Computer Electronics" by Albert P. Malvino, I found this circuit on page 121, figure 8-22(a). It claims to be an example of a discrete TTL ...
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52 views

how to calculate vb1 and vo in this TTL circuit?

By referring to question (i) how to calculate Vb1 and Vo? can i assume Vb1=Vbe(sat) and Vo=5v?
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1answer
35 views

Implement boolean expression with AOI

Below is a question in my homework: \$F(P,Q,R,S,T)=(P+Q)S+(R+T)\bar S\$ using one or more 2x2 AOI."> Here's my attempt for (a): Step 1: simplify boolean expression. \$F(P,Q,R,S,T)\$ \$=(...
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75 views

Why does adding this low pass-filter to a monostable multivibrator prevent triggering?

A 24 VDC sinking sensor is tied to an SSR. The SSR converts the signal from 24 VDC to 5 VDC. The output of the SSR goes directly to input B of a 74121 One-shot. (The diagram has a resistor and ...
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1answer
44 views

1 TTL IC -> inverter + 2-input NAND + 3-input NAND

I came across this question in my homework: Implement the following gates using only one TTL IC: one inverter, one 2-input NAND and one 3-input NAND. The type of IC they're talking about has 14 ...
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30 views

Reverse Feedback protection in a RC circuit

I have been working on a model CPU build from LS TTL ICs for the past couple of weeks. I am going to give a little background here, during the prototyping I stumbled upon several intresting issues ...
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1answer
67 views

Can I use a ST-LINK V2 as a universal JTAG or TTL serial interface?

I have a ST Link V2 as pictured below. I would like to use it as a general purpose JTAG and or Serial TTL USB interface for communicating with a wide variety of devices. The documentation claims it ...
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1answer
67 views

TTL to NIM logic translation Logic Gate Issue

NIM is a standard used in nuclear physics. I'm facing an issue with a logic gate being used in my TTL to NIM translation circuit, and I'm not sure what is entirely wrong with it. For a little ...
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82 views

Can I use a cheap logic analyzer as a USB to UART TTL cable?

I need a USB to UART (TTL) cable for connecting to an onboard JTAG connector. Since I already own a Sigrok logic analyzer, I figure it might function soley as a USB to UART cable. Is this possible? ...
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52 views

TTL 10µs wide generation on CMOS rising edge?

I want to use a DG645 from Stanford research to trigg two different laser. To do this, I need four 10µs negative TTL signal. The DG645 send +5V CMOS signal (picture below). Since I have a little ...
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2answers
73 views

74LS181: Maximum output current?

It seems that I fried my 74LS181N ALU, though I'm operating on 4.95v and have a 1k resistor (plus LED) on all output pins. I was sure it could handle those 5mA, but the datasheet suggests an output ...
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56 views

Voltages at nodes in TTL logic gate

I'm trying to answer the question that has been given here. I think I understand which transistors are on and which are not under the two different logic states i and ii. However, what I really ...
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39 views

Signal conversion LVDS, RS422 and LVTTL

What are all the parameters required to LVDS to lvttl, RS422 to LVTTL and LVTTL to LVDS and RS422 signal conversion?
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Deciding between ULN2804 or ULN2803 with 74HC595

I'm making a circuit with Arduino + 74HC595 + (ULN2804 / ULN2803) to drive a few 12 V Motors. I'm trying to decide whether to use the ULN2804 or ULN2804. On testing, performance of both is fine, ...
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How to connect STM32F103C8t6 to computer when using USART? [closed]

I'm an electrical engineering student and I've just started to learn microcontrollers.I want to know is there any way to connect my board(I uploaded its picture)to computer when I'm using USART ...
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68 views

What DC Power Supply Do I Need To Get For This Device?

I recently bought a small 3 to 1 HDMI Amplifier Switcher. It can work without power adapter only if the 3 HDMI inputs are connected and supplying current. I want to operate it with only 2 input which ...
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1answer
66 views

Why cannot I use the USB port directly to communicate via PC with STM32F4-DISC

I will keep it short and clean, if it won't be enough please let me know and add more details. When using an Arduino UNO, a serial communication can be achieved by the same USB connection which is ...
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1answer
104 views

If you wire together two TTL outputs, which one wins?

If you connect together two outputs from 7400 NAND gates, which output will dominate - high or low? Background: I'm reverse-engineering a 1969 circuit board, and in multiple cases they tie together ...
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1answer
61 views

Will SN74HC245N transceiver support TTL RX when blocked?

I'm actually designing a system with: ~10 "Master" boards that transmit data from slaves boards to a RS485 network 4 "Slave" boards per master one, connected trough a 3 pin jack (5V, GND and half-...
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2answers
122 views

What's the difference between 74LS00 “gates” and 74LS37 “buffers”?

The TI 74LS00 is "quadruple 2-input positive-NAND gates" and the 74LS37 is "quadruple 2-input positive-NAND buffers." The pinouts are identical. The LCCC package is documented exactly the same for ...
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49 views

What's the phase relation between the sine wave and the sync output from a function generator?

I'm using a function generator to generate a sine wave, and am trying to use the sync (TTL) output to flash an LED at the beginning of each wave pulse. However, when I compare the sin wave and the ...
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1answer
85 views

Fundamental TTL circuit and its operation

So i am studying TTL circuits and i started with fundamental configuration as shown in the following picture. NOTE: Transistor Q1 is actually a two emitter transistor, i just couldn't find proper ...
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1answer
58 views

3.3V TTL is dropping to 2v when connected to pin [closed]

3.3V TTL is dropping to 2v when connected to pin. can i use a current limiting resistor in series to maintain 3.3v. Need suggestions.
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791 views

Does this circuit have marginal voltage level problem?

As a research for the problem I described here I found this circuit by Maxim: This is clock doubler, and must be a really good fit in my case as input frequency is very well defined. However looking ...
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1answer
60 views

FT232R TTL Logic Levels

I have an FT232R chip hooked up to my oscilloscope with the TX and RX pins joined. I'm sending characters directly to it via Putty. The logic levels I am seeing are 5V low and 0V high. I thought the ...
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3answers
205 views

MAX232 Replacement

I have a circuit where a 12V square wave signal (a Profile Ignition Pickup signal from a Ford EDIS ignition module) was fed to an MCU via a MAX232 chip. My understanding of the MAX232 is that the ...
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99 views

Switch between USB and Bluetooth module TTL

In my project I have an MCU that I want to communicate with via 5V TTL serial. I have two methods of doing this in my circuit, USB via an FT232R (5V) and Bluetooth via an HC-05 module and level ...
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1answer
33 views

Pull down for 74HCTXX series logic ICs

I am building an adder with standard 74HC/HCT series logic ICs. I see the result when input pins are left floating are erroneous. Shall I have to connect some pull down resistors. Thank you.
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61 views

What specs does the “gros condo” (big capacitor) needs to have?

I have a pair of Dynaudio Air 20 at home. Unfortunately, the cable that used to control the speakers via RS232 died. I opened the cable, and saw that it was a customized RS-232 to TTL adapter, but ...
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49 views

Setting measurement points of the 74HC86 delay time

simulate this circuit – Schematic created using CircuitLab I'm measuring a propagation delay and transition delay of a 74HC86 chip. I setted somewhat high frequency square-wave signal(100kHz) ...
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2answers
109 views

Component recognition from marking code

I need help to recognize a dead component from a lab instrument control board. It is part of a TTL-serial interface, arguably a logic gate or some level shifter, in a TSSOP-14 package. You can see ...
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1answer
42 views

Unpowered 74ls chips vs Powered Nano?

I have a power-hungry 74ls digital logic project that I want to connect a USB-connected Arduino Nano to, but I'm not sure how design the interface between them safely. The project has an external 5V ...
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2answers
114 views

Converting a variable frequency to TTL HIGH and LOW levels, based on a fixed (possible non-fixed?) frequency

I have a square output from an LM324 op-amp (0 and 5 volts) which has a frequency between 1 to 500 Hz (yes, low frequencies). I would like to find a simple way to have HIGH TTL signal when it is over ...
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1answer
87 views

Supplying TTL Signal via USB

I have two pieces of hardware I'd like to interface with via USB. The first are 2002 Series Actuated Valves and the second is a Mass-Flo Controller for regulating gas exchange. To my (admittedly ...
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4answers
132 views

TTL Logic for displaying large 7-segment values [closed]

For fun, I was trying to imagine how I might implement large values in 74 series logic (or any commonly available discrete logic from the 1970s). An example might be displaying prime numbers up to ...
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3answers
87 views

TTL square wave inverter adjustable duty cycle

I am an amateur and I don't have experience with logic circuits so please forgive me if this is very simple. I have a 5V TTL crystal oscillator (4-pin). I need to create a second square wave from it ...
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1answer
146 views

STM32F407 CMOS or TTL or HC

I wonder which logic technology is STM32F407 MCU based on.. CMOS or TTL or HC or LVT etc? Although its mentioned in the datasheet that the GPIO's are CMOS and TTL compliant. I am concerned about this ...
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3answers
271 views

Interfacing GPIO 3.3V to 74HC04 5V

Will it be safe if I connect STM32F407 GPIO outputs (Vdd=3.3V) to 74HC04 hex Inverter inputs (Vdd=5V)? What is the best recommended method to add an inverter at the output of STM32F407 MCU? edit: ...
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1answer
109 views

PL-2303TA TTL UART data corruption

For a lot of projects, I use a fairly common USB to serial dongle called "Prolific USB to Serial" which uses a PL-2303 TA chip to allow USB to 3V TTL serial (i.e. this kind on Alibaba). I actually ...
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5answers
112 views

Will this 555 circuit prevent a car from disconnecting power to the radio when starting?

To start with I'm a little rusty with electronics, I haven't done much in 20 years and it was only a hobby back then. In my car I have a head unit with a touch screen which relies on software to run ...
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2answers
115 views

Can a TTL LS device (low-power Schottky) serve as an input to a basic TTL device?

A 74121 (One-shot) worked well as a reset to a counter device. There is an enable line using a 7400 NAND gate to allow or disallow the trigger to pass. While duplicating the circuit, I found that all ...
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288 views

What is the point of 2 inverters in series? [duplicate]

In the datasheet for the Nexperia HEF4543B, in the logic diagram, there are 2 inverters in series: What is the point of these inverters in series?
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403 views

Can't type on Virtual Terminal Proteus

I've connected my SIM900a module with PC via a USB to TTL converter. I'm using Proteus Virtual Terminal for check the AT commands. The problem is I can't type anything on the Virtual Terminal. Copy ...
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83 views

Why can't I get the output of a 74LS221 to idle at 5 VDC?

I have an industrial machine with an encoder feeding a Measurement Computing USB-CTR08 counter board. In order for the board to count the pulses the counter's gate ...
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3answers
126 views

TTL IC logic high output doesn't reach high enough voltage

I've been having a problem trying to build a breadboard circuit. The problem being, that some IC high outputs doesn't reach a high enough voltage, staying around ~2V. That is not sufficient for a ...
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1answer
37 views

Initial noise prior to square pulse

I have a high voltage system (~5kV) to generate pulsed spark. I was able to detect the spark ignition. It has been shown in the images by the yellow line. This signal will be used to generate another ...
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2answers
94 views

Are there still programmable clock synthesizers with single ended TTL output leves (in 2019)?

I'm looking for a clock synthesizer IC that can drive my vintage 5V NMOS CPU in the range of 5 - 50MHz. The granularity would preferably be in the range of 100kHz or less. All I can find when ...