Questions tagged [darlington]

A structure containing two of the same BJT, used for its increased current gain compared to a single BJT.

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541 views

Sziklai Darlington Transistor Configuration

I'm building a infrared 38khz emitter and I would like to use 4 or 5 LED in multiples directions. I found this article, where in the end it shows a Sziklai Darlington schematic and dont use resistors....
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728 views

opamp heating in voltage controlled current source

Well, I have a serious problem with heat in my circuit. I was trying to build a voltage controlled current source. Everything went fine in the building process. But when I turn ON the power supply the ...
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1answer
897 views

Why does a 2N2222A Darlington pair have 1/2 the hFE as a single one?

I set up a darlington pair out of 2 2N2222As, each with a DMM hFE of 300 or so, and the resulting hFE is 170. I read on the Interwebs that a Darlington can multiply or add the hFEs of the individual ...
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284 views

QUCS Darlington pair

I'm modeling a Darlington pair in QUCS to understand better how to use it in practice. The model is below: The DC analysis predicts a current in the base of T1 of about 1uA and a collector current on ...
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969 views

Darlington Transistor Saturation voltage question

I have been reading the datasheet of TIP122 darlington pair transistor. I am confuse over the term "Collector-Emitter Saturation Voltage". It says it could be 2V or ...
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97 views

How to test if a, in circuit, complementary darling transistor is still functioning properly?

I think a transistor broke down. My knowledge of electronics is not sufficient to solve my issue, so it seems. Hopefully some better educated mind can help me on this. This question is about ...
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1answer
398 views

Circuit to boost PWM voltage using ULN2803a

I am trying to convert 5v PWM signal to 10v using ULN2803a IC. My target device (a dual channel LED light)expects two 10v pwm signal and GND via a 3.5mm audio connector. The part I am struggling with ...
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361 views

Darlington Transistor Array Overheating and failure

I own some animatronic robots that use solenoid valves to operate their mechanical movements. Recently I created a pcb that uses three 8 channel Darlington Arrays ULN2803A to control the individual ...
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784 views

Darlington Transistor functionality

After looking at the schematic for this particular darlington transistor (see picture pasted below) I had some questions about basic functionality. First, the diode at the top right of the picture ...
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4answers
2k views

Push-pull power amplifier on complementary darlingtons

I decided to make a power DC-amplifier. I used complementary darlington pair TIP142 and TIP147. Also TL082 used for negative feedback. The schematic is as below: I gave 100 kHz sine signal and under ...
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560 views

Power dissipation in a Darlington built with an optocoupler and NPN

I have implemented a PWM control over a relay from an Arduino. To isolate both circuits I have used an optocoupler 4N35 from Vishay. Since it cannot provide enough current flow to drive the relay, I ...
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1answer
1k views

Solving Currents in BiCMOS Darlington Pair

Using KVL and assuming that the BJT is in forward-active and that the MOSFET is under saturation and using the given, I was able to generate three equations with three unknowns: 1) \$\frac{3V-2V}{...
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461 views

What are the differences between these Darlington-like circuits?

I built these two circuits. Both of these are Darlington-like circuits, using two NPN transistors in conjuction with each other to generate a much higher gain. simulate this circuit – ...
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1answer
801 views

Adding Darlington transistor in parallele to increase current does not work

I have a circuit that must provide PWM to a motor which is expansive in current (around 1.2 A for 4.5V). For the moment I use 100% duty, but I cannot reach the same efficiency as the one I get when I ...
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1answer
978 views

3.3V SMD transistor to switch HF152F relay

I am an Electronics Hobbyist. I have always been using TIP120 to switch relays. Now for a project, I want to switch a HF152F relay using a 3.3V signal. The transistor has to be SMD and switch using a ...
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139 views

Misunderstanding of amplifiying a current with transistor

Electrical books say that we can use transistor to amplifying current but when I simulate a circuit in proteus input current, it is smaller than emitter current but why? This is a common collector ...
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1k views

Driving IRF540N with darlington

I'm trying to drive MOSFETs with 3.3V PWM signal. Here is a (probably bad) circuit: I know that a darlington is not the best thing to drive a mosfet with. But actually I need to drive many of them ...
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1answer
275 views

Beta reduction capacitor in Sziklai Pair speaker driver

Final installment (promise!) in my set of metal detector circuit questions. This time it's the speaker driver (see images below). When I first saw this, I thought - no problem it's a sziklai pair, ...
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424 views

How to localize cause of short circuit in proto board design?

I'm working on a basic application with a microcontroller controlling several components including a: 12V DC pump (Darlington array) 12V PWM fan (Darlington array) humidity sensor (I2C) and LED ...
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1answer
529 views

AC motor speed controller (via frequency)

I'm building this circuit from an old schematic for a stroboscope (spins a disk with patterns on it and strobes a light based on input frequency). I've already built the frequency divider (it is ...
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1answer
444 views

Driving a DC motor (in one direction) with a microcontroller pin and an opto-isolator

I'm supposed to design a circuit for driving a DC motor with an opto-isolator and a microcontroller pin. The motor is supplied with 12V, and its power is 5W. The opto-isolator has to isolate the ...
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4answers
5k views

Problems with uln2803 darlington transistor array

I am using a few ULN2803's to control LED's. The pin connections and circuit that I am using are shown in the figures below. When a HIGH signal is sent to any of the inputs of the transistor array, ...
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1answer
498 views

Darlington pair open circuit output behaviour

I have a GPIO driving a logic inverter which is then connected to the input of an NPN Darlington pair IC (ULN2803). The MCU and inverter are powered by the same 3v3 rail. I am seeing behaviour which ...
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4answers
331 views

Unexpected 2N6388G Darlington Transistor Emitter Voltage

I'm doing some experimenting with a 2N6388 Darlington Transistor, and getting some unexpected (to me) results. It's been a while since I've played with a raw transistor, so there's a very real ...
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349 views

Is it possible to drive 120 solenoids from 120 outputs of shift register 74HC595?

I want to drive 120 solenoids from 120 shift register outputs. I am driving solenoid by using TIP120 Transistor. When i connect all the solenoids Shift register circuitry heating.
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1answer
245 views

Finding the output resistance of this circuit

I have a BJT Darlington pair with resistances connected to the base and the emitter. I want to know its output resistance seen from collector. I drawed the circuit that needs to be solved for this: ...
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1answer
524 views

Voltage to current converter

In the circuit diagram, R11 is the DUT across which current needs to be measured. According to tests performed on the device, the output current is 1A for sinusoidal input of amplitude 10V and ...
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2answers
627 views

Why are the collector and emitter on this TO-92 transistor reversed?

Every TO-92 BJT I've ever seen reads collector-base-emitter when read left-to-right facing the flat side. Then I found this lovely part, BC517. It reads emitter-base-collector. Have I only been ...
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7answers
10k views

Is there any reason to use junction or Darlington transistors for power applications?

In quite a few Arduino examples, you see people using junction transistors to power a motor. In this case, for example, he's using a Darlington transistor: http://www.instructables.com/id/Use-Arduino-...
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1answer
3k views

MC34063 P-MOSFET driver?

I've got a successful buck converter design using an LM3485. It's got a MOSFET gate driver output pin that swings between Vin and Vin-5V - perfect. My MOSFET is a SQ1431EH-T1-GE3. It has a maximum Vgs ...
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4answers
3k views

Calculating Base Resistor for Darlington Pair

So I know lots of people have asked this question but the more answers/threads I read the more confused I get because people explain it so differently. My confusion is why do I have to even use the ...
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2answers
2k views

Darlington-pair transistor power amplifier for cd-player

I want to build simple one-transistor power amplifier for cd-player. I found 2sd605 Darlington transistor for it. I use 8 Ohm load speaker and have a lab power supply 20V. I want to connect speaker ...
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1answer
331 views

Relay driver from microcontroller

I have put together the following circuit to drive some 12V pumps from a micro-controller using a ULN2003, but it has a few issues. First issue is that the relays click in immediately. I want the ...
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1answer
2k views

What limits the current in a Darlington pair?

I am unsure how the TIP120 doesn't blow up in the given equivalent circuit from the datasheet: I understand that the user will probably use some sort of current limiting resistor before the left ...
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3answers
4k views

Possible to drive a ULN2003 driver with a LM3914 Bar graph display

I would like to drive up to 10 LED's of each pin of a LM3914 Bargraph IC. In my toolbox I have a ULN2003 Darlington drive which ...
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1answer
178 views

Signal parameters of a Darlington

I have the next circuit simulate this circuit – Schematic created using CircuitLab \$V_{BB}\$ and \$V_i\$ represent the output voltage of a previous stage of a circuit. Assuming that \$\beta = ...
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1answer
816 views

Choosing between a darlington array, H-bridge, and solid state relay

I'd like to use an arduino to switch four separate lamps independently, each of which requires 12VDC and 200mA. It seems to me that this could be done with an H-bridge, a darlington array, or solid ...
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What does it means 100v, 10A ,100W darlington transistor?

I want to know what is the relation between (100v, 10A) and 100W in darlington transistor or actually any power device like mosfet or bjt transistor does that means I can use this transistor to drive ...
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1answer
363 views

4N32 Opto-Isolator Questions

I am looking into using a 4N32 opto-isolator and am struggling to find information on its pin 6. This looks to be the base of the transistor (darlington). I see example circuits where they appear to ...
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1answer
559 views

Is it possible to sink and source from one output pin using a darlington driver

Sinking and sourcing with a darlington driver I asked a question about sinking and sourcing LEDs while using a darlington driver. The images were slightly unclear so i have redrawn it. I had too many ...
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3k views

BJT power dissipation - Which value to use? (Ta vs Tc)

I'm using a TIP120 (Darlington pair BJT) brought to saturation for a project of mine. I have \$V_{CE(sat)}=1V\$, \$I_C=2A\$, \$V_{BE}=2.5V\$ and \$I_B=0.005\$A, which give me a total power dissipation ...
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580 views

Esp8266 and uln2003 restarts

I am trying to drive 6 LEDs from an Esp8266 (esp201 break out board). Because of the Limit current of 12 mA the esp can do i want to use a 7way darlington Array to Power the LEDs. I have programmed ...
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140 views

BJT's two stage amplifier

Good evening. Sorry for my grammatical errors, or any other errors that have connection with English grammar and language in general. I have a little problem to solve. I think that these two BJT's ...
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1answer
997 views

H-bridge with BJTs: why do IC and discrete solutions differ (or Sziklai vs Darlington)

I've noticed that [now mostly defunct] discrete BJT combo packages for H-bridges (for example Sanken made a bunch of these, see STA474A schematic below [half-bridge shown]) as well [higher power] ...
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1answer
4k views

NPN vs PNP at H bridges

Lots of different darlington pairs datasheets indicates that NPN are faster(lower rise and fall times), stronger(has a higher Hfe and bigger current maximum) and because of gate source tension, easier ...
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1answer
2k views

What is this circuit equivalent to?

Connecting a small-signal N-channel MOSFET and a power NPN BJT like this darlington-ish configuration, what does it produce? Is it equivalent to what people call IGBT? What about its P-channel ...
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804 views

Circuit for switching LED with minimal impact on digital signal

I am looking for a ciruit which allows switching an LED according to a digital (bus) signal. The actual signal should only be minimal affected (rise time etc.). An example: Light up an LED when a SPI ...
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81 views

Find high current latch or use Darlington array?

Looking for best practices here. I'm building a common-anode LED matrix. I've got a current sink LED driver, and I'm looking for a latch that will provide enough current to drive an array of LEDs. All ...
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1answer
292 views

Controlling a 8A DC pump with a PIC

I need to activate a 12VDC, 8A diaphragm pump with the output of a PIC16F628 (5VDC, 0.025A maximum). The standard way to do it, as I learned in college, is to saturate a transistor that will drive a ...
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2answers
175 views

What it is the maximum “real” current by the collector that can be drawn from ULN2067B

I am building a 5-volt-to-24-volt DC converter using ULN2067B. According to the datasheet this device can support 1.5 A per darlington per collector. Does that mean that all the darlingtons can ...