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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464 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
681 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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2answers
130 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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1answer
767 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
220 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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2answers
393 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 ...
2
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1answer
324 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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0answers
258 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
4k 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
277 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
213 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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2answers
228 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
180 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
414 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
364 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
6k 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
2k 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
2k 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
1k 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
191 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 ...
3
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1answer
1k 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
3k 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
121 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
547 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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3answers
1k views

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
311 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
469 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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2answers
2k 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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0answers
539 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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2answers
124 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
764 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
3k 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
1k 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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2answers
428 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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0answers
73 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
238 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
174 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 ...
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4answers
3k views

Why are NPN Darlington transistors used to sink current?

I notice that NPN Darlington transistors are commonly used to sink current. Wouldn't it make more sense to use PNP for the purpose? This would avoid shunting the load current through both junctions at ...
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2answers
810 views

10 3W RGB LEDs in series control current

I'm having the following schematics connected to a 5V 25A DC power supply. All LEDs are 3W RGB, additional values are. R1: 6.8 ohms 1/2W R2: 4,7 ohms 1/2W R3: 4,7 ohms 1/2W I'm using an Arduino Mini ...
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2answers
2k views

ULN2803 not working properly in Proteous?

I'm trying to test ULN2803 with Led MATRIX. But with different Logic it is giving no change on the output and making the LED lit up. Why is this so
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3answers
625 views

Kn2222A darlington pair + a relay, not functioning at low currents

As the title explains it, I have Kn2222A x2 transistors connected as a Darlington pair connected at the ground side of a [JQC-3F (T73) 5v] relay The relay is connected to a 5v power supply. the ...
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2answers
739 views

ULN2003A to sink current when collector volatge less than base voltage

I am trying to drive a opto-isolator using ULN2003A. My question is that the ULN2003A datasheet here only states the maximum voltage that can be sinked, which is 50v. In my application, the voltage ...
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1answer
123 views

Leave Darlington inputs unconnected

I'm designing a relay-driver board with 15 double throw relays. I'm using shift registers to save IO-pins on the CPU. The shift registers feed into darlington ST ULN2003A transistor arrays: http://...
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2answers
458 views

Sink current for TLP521 via 74HC595 or ULN2803A

I have a TLP521 driving a set of relays. The circuit is shown below. To switch on the relay, I will need to sink the current to complete the P521 circuit, which will trigger the relay. I am ...
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1answer
176 views

Darlington does not switch

I have a darlington Transistor circuit. Like in the schematic i attached. When i power up the 3V3 from my raspberry, the led is not on. When Doing Danke same with 12v instead of 5v, it Works perfectly....
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1answer
607 views

Might I be better off using a TIP122 Darlington than a FQP30N06L MOSFET?

This is a followup to: Simple ESD protection for MOSFETS I built the circuit described in the above post using FQP30N06L MOSFETs and after several hours of testing two of the MOSFETS died at nearly ...
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1answer
173 views

Need to choose between 48 solenoids, trying to design a proper circuit to do so

I am in the process of designing a project that will allow a Raspberry Pi to "print" to an old (60s) electric typewriter. I have decided to have a push-solenoid for each key (24V), for 48 total keys. ...
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1answer
369 views

555 and output amplifer with different Vcc supplies

I want to increase the power of the push-pull amplifier in this circuit. The left 555 generates a square wave and the righthand 555 is triggered by it, and the output of both is amplified by the pairs ...
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1answer
101 views

Controlling 1.5V motor using microcontroller output

I want to control a 1.5V motor using a microcontroller output. The motor draws about 450mA stall current. I am considering to use a Darlington transistor such as TIP120 to bridge the microcontroller ...
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2answers
817 views

Darlington Transistors ULN2003APG Base Voltage

I want to control a 30x1 array of pins through a raspberry pi B+. On a breadboard, I set up a series of shift registers (74HC595) to an array of 2V leds, which I can control as intended. After the ...