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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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 ...
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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 ...
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30 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 ...
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50 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 ...
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69 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 ...
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45 views

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 ...
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5 wire, Logic Output Photointerupter/Slotted Optical Switch

I am trying to get a digital output from a 5 wire photointerupter. The p/n is OPB903w55z, it is configured as an inverted open collector. I have used 4 terminal transistor output photointerupters ...
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77 views

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 ...
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87 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 ...
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72 views

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 ...
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128 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 ...
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48 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. ...
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115 views

Did I get this BJT configurations correct?

I'm trying to learn what kind of BJT transistors are this: Did I get them right?
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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 ...
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88 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 ...
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Connecting unused input 74LS07 gate

This is open collector gate. I can not find the amount of the leakage current through the input. Also not clear what output configuration must be to minimize current: leaving it floating - then with ...
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190 views

PNP Open Collector output series resistor

I have the following circuit to drive a logical output (the input is driven by an MCU): The issue I have is that because of R4, when I want to draw a few mA from the output, the voltage drops. Right ...
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191 views

Open Collector to drive PNP without Pull-Up

I need to generate a current signal between 12V and GND, which has to have galvanic isolation. For this, I want to use an optocoupler. Maximum permittable rise / fall time: < 1µs Output side Vcc: ...
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Why is open collector output is called high impedance and what determines the upper limit of the pull-up resistor?

Is calling open collector output as high impedance due to the value of pull up resistor or due to the fact that the IC itself do not source any current? And what determines the upper limit value of ...
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169 views

IR2110 - Open Collector Output Problem

I'm trying to design an inverter and I'm using 2 IR2110 as gate drivers but my MCU board PWM outputs are open collector, I've added a pull-up and transistor to feed IR2110 with 5V pulses but it's not ...
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208 views

ULN 2003 open collector

I have searched for troubleshooting the ULN and did not find any solution. I use a ULN chip in a motor inverter for controlling precharge relay and main relay. The problem is when the motor inverter ...
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236 views

Are activated open-collector and open-drain circuits wasting energy?

Consider the following reference circuit for a 6N137 optocoupler. My understanding is that this circuit uses a pull-up resistor on the output node so when the optocoupler led is activated, the ...
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181 views

Identify this open collector serial protcol

I'm trying to analyze the serial link between two devices, respectively a motor controller board and a Li-Po battery manager, which battery powers both devices. The application is a battery-powered ...
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591 views

connecting Open drain and Push pull outputs to drive the same pin

I am designing a circuit in which has a voltage supervisor (MCP121-33)with active low output nRST connected to RESET input of the microcontroller which is straightforward. Also, there is a another ...
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57 views

LP311 collector remains at ~11V when “low”

Okay, I'm trying to monitor current going to a device, and in case current is drawn, light a led and provide a low signal (<5V) to a microcontroller. The current goes through a half-ohm resistor ...
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334 views

Connect two different sources with two Digital Ouptuts using an Adam 4055

I would like to operate an Adam 4055 module to control two different applications having their own power supply. Adam 4055 is Digital Input/Output control module over RS-485, I use only the DO part ...
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1answer
133 views

prox sensor with NPN open collector output or a dry contact

I am totally new in this field. I want to use a 5 V / TTL signal from a National Instrument to switch on/off a Red lion PXU series temperature controller. But this controller required a dry contact ...
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345 views

How connect a open collector output to led and to GPIO?

I want to use this Single Cell Li-Ion Solar Battery Charger (BQ24210). The pins /CHG and /PG are an open collector outputs and it will be connected to two low power LEDs as shown in the schematic. If ...
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331 views

Using open collector output from fan sensor to opto-isolator for MCU GPIO

I have a cooling system that uses an external temperature sensor to turn on two HDF4020L-12HHB 12VDC fans and I need to use the locked rotor sensor outputs from the fans as inputs to a MCU (5V logic) ...
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98 views

Is this optocoupler-based circuit design reliable?

Hello, I have designed this optocoupler interface to an stepper driver. However, I'm not sure if it's all right. For R1 I made (5-3.3)/10mA ≈ 180 ohms. 3.3V taking into account the two leds voltage ...
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1k views

May I connect two open collector outputs in parallel

May I connect two open collectors like this in parallel? simulate this circuit – Schematic created using CircuitLab
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Using Raspberry Pi to read open collector outputs from tally connector

Please forgive my ignorance, I'm a software programmer who is new to the electrical and hardware side. Our Panasonic HS300G video switcher has a Tally connector. Below is the pin diagram and circuit ...
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Confusion with the reasons collector area being greater than the emitter region

Often I come up with the following reasoning when it comes to why collector has larger area than the emitter: For less power dissipation collector area should be more. In other words, when area ...
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How can I interface a Raspberry PI GPIO to an open collector circuit to send / receive data?

I have a GPIO from a Raspberry PI connected to a Nintendo 64 system like so: From what I've gathered and observed, the data line on the N64 system is an open-collector output. The line is tied high ...
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How does the Nintendo 64 detect a controller is connected?

To give some context, I am trying to emulate controller input to the N64 via a GPIO pin on the Raspberry PI. In an attempt to accomplish this, I have one of the PI's GPIO's in a pull-up configuration ...
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3answers
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Open Drain Serial TX output on Arduino

I have been trying to implement an open drain Serial output using a Arduino Nano. In the following example I have used 2 Arduino Nanos (both operating at 5V Vcc), using one Arduino as the transmitter ...
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653 views

Why is there no open-collector OR-gate in the 7400 series? [closed]

I searched in the "List of 7400 series integrated circuits" on Wikipedia for a open-collector OR-gate, but couldn't find any. The list looks complete, so I assume there is no such chip in the 7400 ...
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921 views

Open-collector comparator with hysteresis and LED indicator at output

I am trying to choose the correct resistor values to make Vout go high when Vbatt falls below 18V and go low when Vbatt rises above 20V. I've built the actual circuit and my measured values are 18.0V ...
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Why do I2C lines use open drain driver instead of tri-state drivers?

My understanding is that I2C lines use pull-up resistors to passively pull up the bus to logic high because the drivers used on the bus are active drivers, namely open collector/open-drain. Since open ...
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2answers
593 views

Impedance matching open collector output

I am designing a circuit that will receive a 20 MHz square wave (LVDS), convert the LVDS to single ended, and drive a 75 Ohm line. I've found some 75 Ohm drivers from TI, but the applications ...
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650 views

Voltage protection of PNP Open-Collector Pull-Down Resistor Circuit

Circuit Consider the following U-Shaped Micro Photoelectric Sensor Panasonic PM-T54P with two PNP Open-Collector Transistor outputs: I chose the supply voltage to be 12V DC. In the place of the two ...
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2k views

Open Collector/Drain vs Push pull

Given the situation where an LED is being used for a status indicator or similar, not toggling quickly. Which is the best configuration for the IO pin, push pull or open drain? As I see it either ...
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490 views

Understanding Proper Implementation Of Open-Collector

I am confused about the implementation of an open-collector circuit. From what I've read, there are many ways to incorrectly wire up an open-collector circuit. Before I explain my confusion, let me ...
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1answer
166 views

Correctly Configuring and Using DAQ Device Digital TTL I/O

I am using a National Instruments USB-6000 DAQ to control some equipment that accepts TTL inputs. Specifically, I have to pull a pin (normally 5V) to low. As I understand it, to do this, I can use my ...
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856 views

Optoisolator With LED in series not working

I'm using an FODM8061 Optoisoltor with and open collector Logic Output. I'm referencOptoisolator Logic Output Question Here's my current circuit: LED 1(on the left) connects to an open-collector ...
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Totem pole vs open collector configuration

Can anyone please explain for power consumption view point only whether totem pole or open collector should be preferred with a bit explanation?
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105 views

Which side of SPI link harness to locate SDO pull-up?

I'm looking for some help/insight into a decision I am making about whether to change a circuit I have built. My slave device requires a pull-up on its SDO (MISO) pin which is open collector. When ...
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2k views

Open Collector Circuit Needs Pull-Up Resistor to Measure Frequency?

I need a little help determining what I need in order to measure frequency from an Encoder containing the attached Open Collector Output. The 5 Volts will actually be 24 Volts in my scenario (this is ...
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2answers
486 views

Open Collector Comparator for Voltage Glitch Detection

I recently ran a round of PCBs which included an experimental circuit to detect short glitches in my input voltages. I attached the schematic for reference: The intent is that C29, in parallel with ...
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Interfacing open-collector optoisolator to 3.3V microcontroller

I have a bit of a puzzle on my hands trying to interface a Fairchild MID400 optoisolator (popular "logic level" optoisolator for mains detection) to a 3.3V GPIO pin. The MID400 is a 5V part [*] and ...