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Questions tagged [darlington]

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

10
votes
3answers
8k views

Resistors within a Darlington transistor

I've been considering replacing a 2N3904 and TIP31C with a TIP102 in one of my circuits (PWM LED dimmer), and have noticed in the TIP102 schematic resistors leading from each of the bases to the ...
8
votes
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 ...
7
votes
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 ...
6
votes
7answers
5k 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-...
6
votes
1answer
291 views

Is a darlington constructed with 2 BJTs fully equivalent to an integrated one?

Is a darlington constructed with 2 BJTs fully equivalent to an integrated one? The reason I'm asking is that there are obvious differences, like the collectors which are separated, and also the ...
6
votes
4answers
934 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 ...
5
votes
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 ...
4
votes
1answer
277 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 ...
4
votes
1answer
1k views

Driving three high power RGB LEDs with PWM, from a 9v battery

I'm building some LED juggling balls. I'm planning to power an Arduino with two AA batteries, and power the LEDs with a 9V battery. I want to drive three of these 3W RGB LEDS in parallel, with PWM. I'...
4
votes
2answers
372 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 ...
3
votes
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 ...
3
votes
1answer
2k views

2N3904 Darlington Pair

I am making a amplifier with darlington Pair with 2N3904. In input i used my mobile phone & additional supply of 5 volt. It simulates well in Multisim11 BUT in real the second transistor gets so ...
3
votes
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 ...
3
votes
1answer
315 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 ...
3
votes
1answer
272 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 ...
3
votes
1answer
978 views

How to use Darlington arrays to source current in a 7-segment display driver

I'm building a driver for a large common-cathode 7-segment display using a shift register and BJT transistors (more details in this question). I wanted to make it more compact by replacing the ...
3
votes
1answer
1k views

Lab supply schematic - negative rail and darlington transistor pair

While browsing the lab power supplies market and watching the price ranges, I've decided that I'd be better off with building my own, since I've got most of the needed parts anyways. I've searched ...
3
votes
1answer
1k views

Help interpreting TIP127 datasheet

I'm trying to build a constant current 2A amplifier using a TIP 127. To be honest, I have a lack of transistor knowledge. I decided to analyze a few existent circuits with a TIP127 and the datasheet. ...
3
votes
3answers
3k views

Darlington Emitter-follower used as a buffer

I have a circuit with a Darlington emitter follower used as a buffer between a common emitter amplifier and a low resistance load (speaker). i wanted to know if this arrangement could alone (with the ...
3
votes
3answers
3k views

Any IC similar to ULN2003A with latch or enable/disable?

I'm working on a project that uses a ULN2003A (darlington transistor array) and I need to enable/disable it. The point is that ULN2003A does not have enable/disable pin. I think that a IC with latch ...
2
votes
3answers
648 views

Npn transistor failed to work

Sometimes after long time working correctly and turning on and off inductive load, Darlington NPN transistor (ONSEMI BD679) which should follow signal (IN4), fails to work and turns on inductive load ...
2
votes
2answers
571 views

Difference between SN754410 and ULN2004 [closed]

I am curious about the difference between SN754410 and ULN2004 and what are the specific usages of both? According to data sheets SN754410 is a is a quadruple high-current half-H driver and ULN2004 ...
2
votes
3answers
10k views

Use of ULN2003 for LED current drive

I'm trying to use de IC ULN2003 to logically drive the current of different LEDs from a logic input. I have searched for the data sheet but i don't understand how the IC works. I know that there is a ...
2
votes
1answer
230 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 ...
2
votes
1answer
67 views

Power loss in an equally distributed parallel solenoid circuit

I have 12 solenoids (12v rated) connected in parallel to two Darlington arrays (ULN2803A). Each solenoid has 88-ohm impedance. The power supply can provide a stable 12V with up to 2A current draw. (...
2
votes
1answer
694 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] ...
2
votes
2answers
132 views

Suitable transistors for adaptive motorcycle light project

simulate this circuit – Schematic created using CircuitLab I am working on something very similar to this, Adaptive LED Headlights – Model 8790 Adaptive 2 as a hobby project. I have controller ...
2
votes
2answers
599 views

H-Bridge with Darlington BJTs, static shoot-through

I have built the following H-Bridge with TIP122 and TIP127 Darlington BJTs: It is made from parts I had around, and I plan to use it for currents up to 2A with a VCC of 12V. Note that 1N4937 diodes ...
2
votes
3answers
969 views

Use Darlington instead of multiple transistors? If so which one?

Using the example half way down a web page titled "Using the BBB to turn on a transistor" I wanted to know if a similar layout could use a Darlington to drive multiple LEDs instead of individual ...
1
vote
5answers
1k views

H-Bridge out of 2 (1 PNP, 1 NPN) Darlington Arrays

I need to control, with a µC, 4 single-coil latching relays and I am exploring various options. My first bet would be a H-Bridge. Since H-bridge ICs are quite expensive and are mostly designed to ...
1
vote
5answers
720 views

Emulating a switch with open drain outputs

I need to replace mechanical switches with some kind of digital switch. Specifically I want to sent control inputs to various arcade games that use standard JAMMA inputs, which are basically switches ...
1
vote
1answer
2k views

Is it practically okay to use darlington triple?

I need to control a very high current in my project. I'm planning to use darlington formation with three transistors. I'm planning to use BQ24450 to charge a group of 12V acid-lead battery. BQ24450 ...
1
vote
1answer
64 views

IR control with Darlington Transistor ULN2003A

I need a simple circuit to control a IR device. I'm quite a newbie with electronics so I would like to know if this circuit is correct because seems is not working. These are the datasheets of IR ...
1
vote
1answer
301 views

Using 2N2222 as level shifter for TIP127: simulation works, circuit does not [closed]

I'm building an H-bridge with complementary Darlingtons, TIP122 and TIP127, as they are cheap and the nearby shop has them (i know about the high power dissipation, it doesn't matter), and i found ...
1
vote
1answer
468 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 ...
1
vote
2answers
172 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 ...
1
vote
1answer
2k views

How to driving small motors using packaged NPN darlington drivers from MCU?

I have this basic circuit of how to drive a motor using a 2N2222 transistor and it all makes sense to me. I found a bunch of cheap ULN2803APG darlington drivers. I am a bit confused on how to wire 4 ...
1
vote
2answers
102 views

Amplifying signal with Darlington not working

I'm relatively new to electronics and this is not my usual field of work. For a bigger project I need to read a flow sensor's (Biotech FCH-C-PA-N) output. The output needs to be processed by an ...
1
vote
2answers
343 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 ...
1
vote
1answer
573 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 ...
1
vote
2answers
659 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 ...
1
vote
1answer
2k views

Having difficulties using a darlington (BD681) to drive a 12V fan from an Arduino

I'm trying to power a 12v fan using a darlington so I can control the speed from an Arduino. When I wire up as below nothing happens, even though I'm sending a PWM signal: Circuit diagram http://...
1
vote
2answers
199 views

Driving solenoid valve using LM358 as comparator and ULN2003

I'm trying to drive a 12V DC solenoid Valve with following diagram. In 1st block the PC input is compared with 2.2V and its output goes to block2 and ULN2003 for driving the valve. The 2nd block is a ...
1
vote
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 ...
1
vote
2answers
389 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 ...
1
vote
2answers
417 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 ...
1
vote
3answers
89 views

Why Does Flyback Current Destroy Darlington Buffered Op-Amp?

I am working on a project where I'd like to deliver variable DC control voltages to a continuous solenoid motor in order to achieve different velocities of actuation. To buffer my DC control voltage ...
1
vote
1answer
195 views

raspberry pi 3 to switch between 2 similar power supplies

I put the following circuit together and it's working fine, but I still want to be completely sure I'm not missing anything. I think I read somewhere that when a relay is used to switch between power ...
1
vote
1answer
190 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, ...
1
vote
1answer
237 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 ...