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Questions tagged [open-collector]

An open collector is a common type of output found on many integrated circuits (IC).Instead of outputting a signal of a specific voltage or current, the output signal is applied to the base of an internal NPN transistor whose collector is externalized (open) on a pin of the IC. The emitter of the transistor is connected internally to the ground pin. If the output device is a MOSFET the output is called open drain and it functions in a similar way.

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What types of outputs apart from Open Drain/Open Collector exist?

I am trying to grasp the idea of an Open Circuit/Open Drain, but I haven't been able to find, which other types of outputs exist ("Closed Circuits", so to speak). It would be helpful, if you ...
Andrew's Quest's user avatar
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Watching an open-collector input without disturbing it

I'm trying to control an opto-isolator (actually a photorelay such as a TLP354x but it doesn't really matter here). The problem lie in an external device (black magic box) which is also controlled by ...
VoltsAndNuts's user avatar
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How to calculate pull up resistor for Power Good Pin?

I am learning to design buck converter. And using LM70880-Q1 buck. There is power good pin is available. I want to make use of this pin. It is a open collector output that goes low if the Vout is ...
Virtualworld 's user avatar
3 votes
2 answers
311 views

How can I make a non-inverting open-collector (or open drain) with a single transistor?

I had a PCB made for a homebrew SBC but while waiting for the boards I discovered a bug. I have a 74HC138 output (I believe this is just normal push-pull) that I need to hook up to a CPU pin but I ...
Procrastin8's user avatar
4 votes
2 answers
476 views

Why don't we use decoupling capacitors for open-drain outputs?

If an IC with open-drain outputs (and hence pull-up resistors) is used, we of course put decoupling capacitors on the IC supply, but why don't we also add decoupling capacitors between the power pin ...
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7407 functional schematic question

I was trying to understand the role of the left-most transistor. ... as illustrated in the datasheet: SNx407 and SNx417 Hex Buffers and Drivers With Open-Collector High-Voltage Outputs If there is a '...
Timothy's user avatar
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2 answers
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Thoroughly confused about open drain

I've been reading a tutorial on open drain and I'm thoroughly confused. First, the terminology makes little sense. How can a resistor pull up or pull down current when its job is to resist current? ...
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Can I drive a relay with a PCF8575?

I would like to drive a relay using a PCF8575, which has "quasi-bidirectional input/output (I/O)" ports. If I understood properly, they are open-drain ports. Is this diagram OK? Do I need ...
aguedob's user avatar
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Best way to use Driveay alert output (Open Collector NPN)

I'm learning as I go on this project. I have a beam-break driveway alert that I would like to get the output from on a device like an Arduino or Raspberry Pi and need some guidance on the best ...
sdg's user avatar
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1 answer
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Control WS2812x from open collector output

I have a board with digital output that is based on open collector Darlington driver (providing up to 500mA) and I want to use that output to control WS2812x LED strip. What should the circuit look ...
0wl's user avatar
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8 answers
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Why should an open drain/collector comparator go low when pull up is not connected if it is essentially a floating node?

As we know the open drain/collector output stage of a comparator looks something like this: This is essentially a high impendance floating node. If we fail to connect pull up, the output does not go ...
needbrainscratched's user avatar
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Pulling 5 V signal line down to 0.5 V

I want to pull a 5 V signal line down to 0.5 V via an open-collector NPN BJT. I intend to implement a simple voltage divider by using a resistor between emitter and ground. The base is driven by a 5 V ...
RenX's user avatar
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1 answer
180 views

Open collector circuit input to logic gate

I'm designing a simple circuit where I intercept and read an open collector pulse signal from an external machine and let it pass through to an optocoupler. In addition to that, I can also output a ...
Max's user avatar
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Open Collector config ULN2003

Are open collector configurations like those found in ULN2003 always in saturation (when Sufficient Base voltage is applied)? Can they never go into the active region?
Harkirat's user avatar
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Cannot handle open collector output

I have a sensor powered at 24VDC which has an open collector output The output of the sensor (it is a PIR sensor), goes from 15Vdc when nothing is detected, and 0.7 Vdc when it detects some movement. ...
D_A_8's user avatar
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3 answers
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Problem with SN7407 output

I'm carrying out an experiment using an SN7407, which is an open-collector output buffer. The use of this IC is to make the pulses (PWM) coming from a DSP (~3.3 V) be sent to a gate-driver circuit (~...
Erick's user avatar
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To drive current with open-collector gate when input is high, do I need a buffer or an inverter?

Once upon a time I knew the answer, or could just try it. But with distance I forgot. When I use an open collector, I do it to drive some load. So High means current is flowing. But when it is used as ...
Gunther Schadow's user avatar
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1 answer
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3-pin SMD Marking VB Part Identification

I can't determine the part number for this open collector.
RubenNaz's user avatar
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1 answer
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Can someone confirm the typical application circuit of MAX664x Fan controller datasheet?

I'm planning to use the MAX 6644 for a simple fan control application. All in all the IC is very straight forward to use. However after analyzing the typical application circuits in the datasheet I ...
Svenito's user avatar
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Why does this solid state relay circuit work sometimes and not other times? (stuck closed)

It's a very simple open collector output from one device driving a solid-state relay (VO1400) in another device. You can see the power transistors (BS868) that drive OUTn.n in the circuit diagram. ...
mikey_jp's user avatar
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1k views

Pullup resistor for automotive protocol like CAN and LIN

I understand that how open collector works on protocol like I2C. However, from my understanding, the automotive protocols like CAN and LIN also use open collector to talk to other devices. LIN is ...
JOSEPH129009's user avatar
7 votes
3 answers
1k views

Tying open-collector outputs to TTL inputs

I know that open collector outputs are effectively either 0 V or high-Z. I also know that TTL chips tend to read a disconnected output as high, but that really you should have something like a 1 kΩ ...
Rob Simmons's user avatar
3 votes
3 answers
276 views

Power Consumption for Open Drain Communication

When using an open drain communication scheme, like I2C, it seems that the majority of power consumption comes from the sinking of current through the pull up resistor when a logic 0 is transmitted. ...
Jake Hertz's user avatar
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Drive NPN from Voltage Regulator?

I am trying to get two disparate camera systems to talk to one another, specifically an Arri camera with a Preston system, and specifically to transmit a tally signal when the camera is recording. ...
zib_redlektab's user avatar
1 vote
1 answer
513 views

5V Device Open Collector with 3.3V Controller

I am new to electronics being a mechanical engineer. My question is this: I am about to use an Allegro A314x Hall Sensor, powered by 5V. Datasheet (link) says, data pin is open collector. I want to ...
dexamenos's user avatar
1 vote
1 answer
376 views

Knowledge requested for WS2811 Based RGB LED driver Module

Design of LED Module based on WS2811 LED driver IC (Only Red-channel is shown). To the right of the schematic you will find a simple, cheap and robust constant current LED driver. The current for the ...
Harry Viet's user avatar
1 vote
1 answer
411 views

How to interface MCU with open-collector output?

I have a 3.3VDC microcontroller (based on Nordic nRF52840) with digital inputs which I need to interface to a device that outputs slow pulses (1 second) via an "open collector output". The ...
Ryan Griggs's user avatar
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5 votes
6 answers
2k views

Difference between no input and a zero input in digital electronics

I'm new to digital electronics and try to understand how logic gates works. In books many times Zeroes​ and ones are referred as Low and High respectively, is Low and High used as an indication of ...
user215805's user avatar
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2 answers
219 views

Minimizing pulled open collector output rise time on 74LS09

I have a circuit that calls for one open collector buffer for driving a shared line (/WAIT via Zilog Z80) and one typical AND gate. I've consolidated these into a single 74LS09 open collector quad 2-...
Bit Fracture's user avatar
6 votes
4 answers
2k views

Why are the outputs of these gates tied together in the Apollo Guidance Computer?

In looking at the AGC schematics, I'm finding a lot of instances where the outputs of some of the NOR gates are tied together when feeding into another gate. The most dramatic example being here, ...
stix's user avatar
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Open-Collector to Push-Pull

In a project I am using a 74LS05 to provide an ESP32 microcontroller with 6 open-collector outputs. Actually this is fine for 5 of the outputs, but for the remaining one I'd rather have a full push-...
SukkoPera's user avatar
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2 votes
4 answers
289 views

Purpose of base-collector resistor in open-collector opto-isolated GPIO output

I've been working with an opto-isolated output for a high-speed camera I'm interfacing with and was a little puzzled by the circuit they were using for an opto-isolated open collector output. As far ...
JulianEE's user avatar
3 votes
2 answers
970 views

When using an open-drain output to drive an NPN transistor, can the base resistor be replaced by a pull-up?

Assuming the value of R1 is the correct value for the base resistor for the given motor L1, is it okay to omit the additional base resistor, used in push-pull applications, for an open-collector ...
Benedikt M.'s user avatar
2 votes
1 answer
81 views

Define the purpose of these components in the operation of this low side driver

I am trying to understand the operation of the following low side driver circuit I found in a schematic of an old pinball machine (redrawn for clarity): L1 is a Solenoid and Q1 is a Darlington BJT (...
Kyle's user avatar
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2 answers
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Can this be done with the TLP2368 optocoupler (open collector)? (Toshiba)

I have tried to write to Toshiba technical service, but no one responds. I have the layout of this optocoupler (TLP2368). According to the datasheets, the VCC voltage to GND is a maximum of 6V, so I ...
Fabián Romo's user avatar
1 vote
0 answers
248 views

Open Collector Output connection to a relay

Hey sorry if this question is too simple, as i am not an expert in this. I have a device ( industrial router, works at 0- 30vdc) which has a Galvanically isolated Open collector ( External 0-30 VDC, 0....
Joe's user avatar
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1 vote
1 answer
115 views

Does the 74LS09 have an adequate internal input pullup?

I want to feed an output of the 74LS05 open collector inverter into one of the inputs of the 74LS09 AND gate. The internal schematics in the datasheet shows that there is an internal resistor and 2 ...
JustClaire's user avatar
1 vote
3 answers
310 views

Connection of two open drain outputs to control common LEDs by PIC32MZ

I want to use this Single Cell Li-Ion Battery Charger (MCP73833). The pins STAT1 STAT2 and /PG are an open collector outputs and it will be connected to low power LEDs as shown in the schematic. If I ...
Tomasz Dzikuć's user avatar
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1 answer
151 views

How to drive pin to open drain/collector?

I'm looking at a datasheet for a bit of hardware I am adding to a design. However, one of the pins on the chip is listed as: ON/OFF - 1.8V must be driven to open drain/collector It does not specify ...
JolonB's user avatar
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1 answer
323 views

Help understanding open collector comparator

I am working on a simple circuit based on the LM311 comparator. It has an open collector, which is not something that I've used before, and I have a few questions. First, my understanding of the open ...
richbai90's user avatar
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1 answer
491 views

Explanation for parallel darlington behavior

I've built and simulated the circuit below in real life, LTSpice and Stack-Echange-Spice. It behaves in a similar fashion in all of these Environments. When the "LAMP2" load is disconnected, the Base ...
Funky Luke's user avatar
1 vote
1 answer
307 views

What is the purpose of this schottky diode reversed across the BJT base resistor?

In a design for the popular "gotek" floppy drive emulator, as per the standard, the outputs from the floppy emulator are open-collector. An STM32 is used as the processor. This drives a 74HC04, which ...
Mono's user avatar
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2 votes
1 answer
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Help on translating 5V rotary signal output to interface with lathe's cnc controller!

I have a hall sensor (OH137 - open collector) as an index signal on my lathe’s spindle. I have the sensor pulled high by a 1k resistor and can’t change it because they’re both glued in epoxy. This ...
Rodrigo's user avatar
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1 answer
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Open collector and open drain logical gates

Can somebody explain what open collector and open drain mean? I'm a CS student, and I'm really a newbie in terms of electronics and I only managed to find some "expert level" explanations, which I ...
MartinYakuza's user avatar
1 vote
1 answer
224 views

Open collector / drain question

I'm trying to to find the best way to force an inverting amplifier to postive saturation with a gate input, but otherwise leave the function of the op-amp intact. I've come up with a few ways to do ...
Jon's user avatar
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1 answer
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Simplest way to short two leads with GPIO

I have a piece of hardware that has an open collector GPIO as shown below: I'd like to have use the open-collector output to short two floating wires together -- they're essentially two leads from a ...
nathan lachenmyer's user avatar
0 votes
1 answer
2k views

Proper use of open collector to switch an output

I'm working with a pre-existing piece of consumer hardware that has an open collector GPIO output, as shown below: The Open Collector is able to source up to 100 mA. I'd like to switch a relay (a ...
nathan lachenmyer's user avatar
0 votes
1 answer
316 views

MCU PIN Open Drain Protection

I am trying to control a PC fan using a micro-controller(STM32F0) According Intel's PWM fan spec, the fan will pull up the PWM signal to up to 5.25V. ...
LD1117's user avatar
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4 votes
4 answers
3k views

What is an open collector?

I am new to electronics, and I'm reading a book on embedded systems and bumped into an "Open Collector". I know that a transistor has a base, which acts like a switch for the current to flow from ...
GoldenRetriever's user avatar
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2 answers
350 views

Adapting the 74LS170 open-collector "register file" to active-high TTL input

This is a question related to swapping a 74LS170 4 x 4 register file chip for a 74LS173 single 4-bit register. In the other question I wonder if there are even simpler ways to Turn a positive clock ...
Gunther Schadow's user avatar