Questions tagged [darlington]

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

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TIP120 excessive voltage drop

I've been trying to make my own H-bridge using a TIP120. With the test circuit below, I was expecting to get ~6V at minimum across the resistor but I'm getting less than 3V. The circuit still outputs ...
Gepeto's user avatar
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6 votes
3 answers
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How is this circuit generating a voltage seemingly from nothing?

I made a Darlington pair from two 2N3904 transistors, and connected the collector (of the entire Darlington pair) to the 3.3V output of a breadboard power supply (powered by an adapter that plugs into ...
16-bit-apps's user avatar
5 votes
3 answers
387 views

Need help with audio amplifier design for loud volume

I'm trying to design an audio amplifier. The preamp stage is a voltage divider CE, while the power stage is a Darlington Class A: My goal is to amplify a \$48.7\ \mathrm{mV},\ 1.07\ \mathrm{mA}\$ (...
Halfy's user avatar
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How to determine the collector current limiting resistors for the Darlington's pair of transistors?

How were the resistors in the circuit calculated?, I would like to come up with a similar circuit but for a 5VDC power supply, and I would like to resize the resistors as per my load requirement, my ...
Ronny Alfons's user avatar
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2 answers
197 views

How to design BJT common collector amplifier?

I am working on a school project and I am struggling to design what is supposed to be an easy CC-amplifier. All other parts of the circuit are calculated and should work. The power amplifier is what's ...
VinFurr's user avatar
2 votes
1 answer
80 views

Problem with Darlington Pair Experiment using Two BC547Bs

simulate this circuit – Schematic created using CircuitLab In schematic (a), the LED illuminates dimly on holding the 2 probes and gets brighter the harder one squeezes. My understanding of why ...
J R's user avatar
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3 votes
1 answer
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Finding Vbe for a darlington pair?

I'm looking for guidance for a homework problem. I have invested several hours into it, and the feedback from the professor hasn't been constructive. I modeled the circuit with LtSpice to verify my ...
Sparky 's user avatar
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2 answers
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Darlington configuration using BJTs [closed]

Does a Darlington configuration using two BJTs, say a BC548, override the total power they could dissipate?
imran muhd's user avatar
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1 answer
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Darlington Amplifier circuit (TIP 120) [duplicate]

I'm trying to wire a darlington TIP120 just to see if I can get the 1000 hfe dc gain at 100mA like it said on the data sheet. I made the circuit like it appeared in the data sheet, but wasn't ...
imran muhd's user avatar
3 votes
2 answers
643 views

Darlington transistor configuration

Can two 2n2222a transistors output more than 1amp of current if biased properly; supposing 1.4v to 1.5v is applied to the base?
imran muhd's user avatar
6 votes
6 answers
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What is the use of the PNP transistor in this circuit?

The schematic below describes the structure of a single channel from the 8-Channel Darlington Current Driver TD62783A. Image source: 8-Channel Darlington Current Driver TD62783A I understand most of ...
Virgil_Tibbs's user avatar
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switching multiple supply voltages on same low-side darlington array IC

Say I have an MCU switching a couple SSRs using the ubiquitous ULN2803 at 5V on the "common" pin, but I'd like to switch a 12V mechanical relay with the same chip as well. Checking the ...
Joe's user avatar
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What is the purpose of the resistors in a Darlington transistor [duplicate]

I come across with a transistor circuit as shown below. Does anyone know what is the purpose of R1 and R2?
user42423's user avatar
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2 answers
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Variable output voltage regulation - does this solution make sense?

I want to use a switching power supply that has a fixed 24VDC output. I want to add a simple circuit that will give me an adjustable voltage between 0-24VDC. The power supply allows the consumption of ...
Jerzy Przezdziecki's user avatar
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2 answers
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Driving 10ch outputs with 5V AVR

I use a 5V AVR (ATmega1284p) to measure some data. Depending on the data I would like to switch one of 10 outputs. Each of these outputs should have a LED (as an indicator and for debugging purposes) ...
Eimer Z.'s user avatar
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1 answer
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Protecting voltage regulator circuit against broken neutral

I have a simple voltage regulator. The voltage input is on the left side and the output is on the right side. Input voltage (Vin) can be as high as 400V (rectified AC) and output voltage (Vout) is ...
Saksham Jain's user avatar
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Microcontroller driven circuit that opens a charging circuit and closes a resistive circuit simultaneously from the same I/O pin

I'm working on a project that charges a capacitor with an external 5V DC power supply and then discharges it across a very low resistance. Since I don't want to close the circuit while the power ...
Rusto Clown's user avatar
3 votes
3 answers
483 views

Increasing current from a linear regulator IC

I'm designing a device that will use a common "yellow" 20V tool lithium battery pack (which I know contains an array of 18650 cells, and is actually an 18V pack,) both for its internal ...
Matthew Clark's user avatar
4 votes
4 answers
3k views

Why don't we use MOSFETs in the Darlington configuration?

Why is it not practical to connect the two drains of the MOSFETs together? Is it not practical to connect the source of one MOSFET to the gate of another?
sixfourfivetwo's user avatar
1 vote
1 answer
246 views

Linear regulator darlington

I don't know if such a regulator should be sinking current in the first place, I can't get any example on the web that shows a similar example of an op amp sourcing current to the base of the NPN to ...
Christopher Otniel's user avatar
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Darlington Pair TIP41C at op amp output not amplifying current

I am trying to make a variable voltage regulator with the TL081CP op amp. When I add a single TIP41C transistor the max current I can get at the 20 ohm 20 W load is about 625 mA. But when I want to ...
Christopher Otniel's user avatar
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1 answer
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How to drive a small 8 Ω load given a CE-CE amplifier?

I want to amplify a 25 mVpp input signal with a source resistance of 1 kΩ to anywhere from 2.5 Vpp to 3 Vpp to drive an 8 Ω load (though at this point I am willing to sacrifice gain to just drive my ...
MeljahU's user avatar
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2 answers
88 views

PNP TIP126 transistor hot to touch while in use

I have a 7-segment mechanical 'vane' display andbgot it working using a circuit originally suggested to me here. The diagram below is a slightly modified version. Each vane draws around 0.2A of ...
user2878409's user avatar
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I made a darlington transistor in LTspice. But, that has different values from theoretical values

As you may see from title, I made a darlington transistor like this. I set each transistor(Q1 and Q2) to have β = 150. So, total darlington β must have 22500 or thereabouts according to a formula ...
user299980's user avatar
2 votes
1 answer
209 views

Is this TIP102 Darlington Transistor Circuit Correct?

Objective: Power on Pi Zero by setting pin 13 of Arduino to HIGH. I plan on using the Arduino to measure the Li Ion battery voltage and, if well charged (so, say over 4V), then it will pull pin 13 ...
ng5000's user avatar
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5 votes
1 answer
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Darlington triplet - static electricity detector?

simulate this circuit – Schematic created using CircuitLab I built this circuit. Different versions of this exist on the internet, some using an MPF-102 JFET instead of the 3 NPNs. The various ...
Annette Gates's user avatar
8 votes
2 answers
819 views

Darlington Triplet

I was playing around in Falstad Circuit Simulator with powering a 2.5V incandescent lamp with a Darlington Triplet. I tried it two different ways and got slightly different results. I'm not sure if ...
Annette Gates's user avatar
1 vote
2 answers
431 views

Switching 3.3V 150mA efficiently

I have a load (from 20 LEDs with 20 resistors) that I want to switch on/off as a single block, using a GPIO pin from a micro-controller. I have measured the current to be 145mA at 3.3V Vcc. simulate ...
Bram's user avatar
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Darlington Transistor hybrid parameters from BJT h-parameters

I'm trying to analyze the Darlington transistor model, so I need to calculate the hybrid parameters for this circuit. For example $$h_{ie} = \frac{v_{be}}{i_b}\bigg\rvert_{v_{ce=0}}$$ So which is the ...
Simone's user avatar
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What does a Darlington pair do in a DC power supply circuit?

I really don't understand the role of the Darlington pair (T1) in this circuit. As it is a DC power supply circuit, I always thought that the pair is useful to have a high gain in audio and AOP ...
Legend27's user avatar
38 votes
4 answers
5k views

What is this unusual NPN-PNP transistor pair?

I was looking for the datasheet for a transistor I'd discovered during some reverse engineering, a DK52T. Unfortunately I can't find its datasheet, but I found one for the DK52D. See the image below; ...
parkside's user avatar
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-1 votes
1 answer
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How to set loading(resistance) when i try to simulation Darlington pair limit current between Voltage 9 to 36

How do I set my loading (R13) value for simulating Darlington limit current between 9 to 36 V? If there is no loading (R13), the result of Q1 current (C to E) would not show correctly, but a placing ...
Ethan Ku's user avatar
0 votes
3 answers
618 views

How does a Zener diode and NPN BJT control circuit provide current limit or thermal shutdown via an NPN Darlington pass transistor?

Background Application: 1995 Ford Ranger Manual Control Blend Door Actuator This 1 page pdf guide shows the block level function of a manual blend door actuator (my component is from a Ford Ranger.) ...
SystemTheory's user avatar
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1 answer
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Unused pins of FMBA14

I am using NPN Darlington array FMBA14. I am only using B1,C1 and E1 pins for my application. The other pins B2,C2 and E2 can be left floating?. Can someone suggest anything on this? Thank you
MightyBeard007's user avatar
0 votes
2 answers
506 views

Replacing Darlington with MOSFET for capacitive discharge circuit into a solenoid?

I have the following circuit and criteria and am wondering if it makes sense to replace the Darlington transistor with a MOSFET, and if so how would that change the circuit? This circuit turns on T1 ...
FDecker's user avatar
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1 vote
2 answers
169 views

Have I understood transistors correctly?

These are what I know and what I've concluded about transistors. Correct me if I'm wrong: It's all about current. When we have a determined voltage differential source, BJTs are used to boost the ...
Elementronics's user avatar
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2 answers
110 views

Simple question about Darlington BJT

I have this circuit for a pasive balancing battery cell with 2 PNP Darlington transistors with switching role. When I close the circuit with the optocoupler the transistors are open. R7 and R1 are ...
Aurel Mănica's user avatar
3 votes
3 answers
3k views

Which one would be better for 3.3V outputs among ULN2001 and ULN2003?

I intend on driving 24VDC relays with darlington arrays of the ULN200X series. Since the darlingtons will be driven by a 3.3VDC outputs I am hesitating on whether I should choose ULN2003 or ULN2001. ...
Phill Donn's user avatar
8 votes
3 answers
379 views

H-bridge failing under load

I have made two H-bridges following this schematic. I have replaced: TIP107 with TIP147 TIP102 with TIP142 The opto-couplers are P785. I have not included the diodes as they are internal to the TIP. I ...
GiuBu's user avatar
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1 answer
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Making a Darlington transistor (eg: TIP120) with D882 to drive 12V LEDs with 3.3V or 5V input RPi

I am getting into circuits and trying to improve my knowledge but even though it might sound like a silly question but here is my story short: What I am trying to do I am building a circuit to drive ...
maxleb's user avatar
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1 vote
1 answer
96 views

Touch switch for hanging lamp (touching metal bar): Ideas?

A few years ago, we have bought an IKEA Glimt hanging lamp that operates with halogen lamps. It has a "touch dim" functionality, so when a person touches the metal bar of the lamp, it dims (...
sophonet's user avatar
4 votes
2 answers
135 views

Darlington biasing design error in a commercial frequency counter oven control circuit?

I am repairing a commercial frequency counter (brand to remain anonymous) that had the crystal oven visibly overheat. There is a small PCB in the oven that holds the crystals, the oscillator circuit, ...
LevelUpEELab's user avatar
2 votes
1 answer
4k views

How to power WeMos D1 Mini without USB?

The title does not tell the entire story. I have successfully powered my WeMos by supplying 5vdc to the 5v pin. My power source is 12v battery so I am using a buck converter to drop the voltage to 5v. ...
Tim Duncklee's user avatar
5 votes
4 answers
1k views

One transistor versus two transistors as a switch

Why does the led dim first and then switch off when I use one transistor as a switch, but directly switch off when I use two transistors as a switch? These are the two circuits:
nsyamimi sazali's user avatar
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0 answers
551 views

AC current gain of an emitter follower configuration with a Darlington transistor and a source resistance

We're using the book Electronic Devices and Circuit Theory by Boylestad for our circuits class and are currently on Darlington transistors. I'm trying to solve the current gain of a circuit with an ...
ARKONITE Requiem's user avatar
0 votes
2 answers
366 views

why could Darlington circuit protect Load Dump at automotive?

I just took over a project from EX co-worker and not understand a circuit (Darlington circuit) designed to against load dump(5b) at automotive. in my previous experience, TVS usually is used for ...
Ethan Ku's user avatar
2 votes
4 answers
450 views

Classic multivibrator circuit and LTSpice, why is there reverse voltage on base even with diode?

I had fun today learning the basics of LTSpice using a variation of the "classic multivibrator" (*). I have also built a working version with real components. There is a significant ...
wsanders's user avatar
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0 votes
1 answer
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Resistor value calculation for optocoupler input

I am working on an optocoupler (LTV-845) circuit. Below is my working circuit: Forward current flowing to opto input would be (Vcc-Vf(LED)) / Rf = (24V-2.1V)/470 = 0.046A. Is my understanding correct?...
user1890's user avatar
3 votes
1 answer
204 views

Strange floating base NPN behavior

I'm learning about NPN transistors and have wired up this: I understand some of its behavior, but one is a complete mystery for me. First, if I tie "B" (green dangling wire) to "G"...
klao's user avatar
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0 votes
0 answers
213 views

Problem in 5v pump

I connected the pump to tip122 darlington transistor to control it via serial port. but the pump doesn't work. instead , it makes sound. how can i make the pump work the circuit of the tip122 : the ...
Kiroloes Amir's user avatar

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