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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.

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20 views

FG servo motor speed issues

I have been trying to get a 40-year-old turntable back to life, with relative success until now. Everything works fine but for an intermittent issue with the motor. The motor has two modes (for 33 1/...
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1answer
35 views

LowPro proportional valve drive circuit clarification

Am new with amplifiers when trying to use them as a current controller so is just after some help in understanding the circuit. I am designing a circuit that will use a LowPro Proportional Valve ...
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2answers
133 views

Are there darlingtons more powerful than the ULN2803A?

I made a card controlling 24 electromagnets with an Arduino board via 3 darlington ULN2803A My power supply for the electromagnets was 20 V and 300 mA for each electromagnet. Due to the physical ...
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1answer
27 views

driving a medium power darlington transistor with the output of a 555 timer

Question: What is the limitation on the output of the 555 timer with respect to the requirements of the input of the BDW42G? Can the 555 provide enough current at 5 volts to trigger (sufficiently) ...
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3answers
69 views

How can I measure a TIP120's beta?

I was promised a current gain of roughly a thousand. We had an experiment involving this circuit to measure the input base current and output emitter current: (That base resistor is a 50k ohm ...
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2answers
94 views

Darlington pair [closed]

Here, the first transistor t1, is to be connected in CC configuration. Doesn't that mean that the collector of the first transistor should be grounded? Also, the collector doesn't seem to be "common"...
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1answer
55 views

Drive a resistive heater from a low power IC

I'd like to drive a resistive heater using an IC operating at 3.3 V. The heater may need to dissipate up to 18 W, and will be powered by a 28.8 V battery. The IC is able to generate PWM signals, but ...
3
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1answer
607 views

Why is the collector current I_c for a normal common emitter BJT circuit LARGER than that of the Darlington transistor circuit configuration?

I'm a noob to electronics and have been reading up on transistors. I tried to simulate Darlington (NPN) and Sziklai transistor and compare them against a single common emitter NPN configuration, ...
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1answer
75 views

Do BJT (Darlington) transistors have a minimum collector current?

I am using a TIP122 Darlington transistor. From the graph provided in the datasheet, I can see that the saturation voltage decreases as the collector current decreases. Since the load I am driving ...
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0answers
56 views

PNP darlington pair calculations

I have a 20ohms discharge resistor connected to my PNP darlington pair. I have simulated the circuit in my mobile (every circuit app).please find the attachment for circuit. But here I'm unable to ...
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1answer
50 views

Understanding the Design of Common ULN2803a Motor Driverboards (use of the capacitor in particular)

I'm studying a popular motor driver board based on the ULN2803a Darlington Array chip (top and bottom pictured below). A capacitor is between the common diode/flyback trace and GND. Does the ...
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0answers
89 views

Darlington Transistor TIP142 same type but different values

I have a bunch of Darlington NPN Transistors TIP142 that are removed from two separate identical boards. The 1st one have the TO−218 CASE (left side of the image) and the 2nd the TO−247 CASE (right ...
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1answer
86 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 ...
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0answers
101 views

Darlington pair. Purpose of components

Giving the following schematic: What is purpose of R1 and the diodes ?
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1answer
35 views

Powering 4 modulated IR LEDs through transistor

I've done some research but can't seem to find an answer to my specific problem. I'm using an Arduino as a beam-break sensor. In order to do that it modulates the IR LED at 38kHz by code and listens ...
1
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1answer
78 views

How to get current flowing through the darlington transistor as a switch for a stepper motor?

I have a 17PM-K307-05VS unipolar stepper motor. I am building the driver for the stepper motor. The exact rated voltage and current are unknown, it seems the motor is old or discontinued, but the ...
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2answers
136 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 ...
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1answer
374 views

Latching/Non-Latching Relay Driver Circuit with darlington optocoupler

I'm designing a circuit where an ESP8266 controls two types of relays, a single coil latching relay and a normal non-latching relay. The relays are power relays use to control low power electrical ...
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1answer
82 views

Need help with a 3 stage amplifier

I am working on my final project for class and am STUCK! I am to design a 3 stage circuit with stage 1 and 2 using a 2N3904 transistor in a votlage divider config. and stage 3 using a darlington ...
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2answers
122 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 ...
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3answers
144 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 ...
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2answers
329 views

Guitar Amplifier Peavey Backstage Plus

The fuse of this guitar amplifier blows. Changing the output transistors had the amp working for a while, but then after a while the fuse blew again. The output transistors that were changed are new....
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3answers
703 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 ...
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2answers
265 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 ...
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4answers
236 views

uln2003a: Switching ground of device works, however, optional USB function of device doesn't work correctly

I use the uln2003a to switch a device (with use of a MCU) that is capable doing several things, like fm-radio, bluetooth, playing MP3's etc. It also provides an USB ...
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1answer
61 views

ULN2803a relay connection

A motion sensor and a relay should be connected with an atmega328p. I soldered my circuit on a perfboard and have 5V power and ground rails on it. Can I use the rail for the COM port of the ULN2803a ...
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1answer
403 views

calculating input resistance of darlington pair (TIP120) from datasheet values

I've tried to find a way to calculate the input resistance of a darlington pair (TIP120), using the values given in the datasheets. https://www.onsemi.com/pub/Collateral/TIP120-D.PDF After Searching ...
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3answers
352 views

darlington transistor led matrix

I want to run an 8x8 led matrix by using a darlington transistor arduino and decoder. for some reference I was looking at this previous question(Darlington Transistor Array). Each of my Leds draws ...
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2answers
414 views

Why is the load on a darlington pair put before the transistors rather than after?

Forgive my lack of understanding and if this is answered somewhere I have not found, but... I have seen lots of answers with regard to how to use a darlington pair to switch, say, a 12V 1A load using ...
2
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1answer
88 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. (...
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1answer
230 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 ...
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2answers
61 views

ULN2002A Not turning on?

I ordered a few ULN2002As. I have it wired as follows: Pin 1 -> GPIO of Arduino Pro Mini 3.3V Pin 16 -> 300Ω resistor in series with an LED Pin 8 -> GND Pin 9 (COM) -> 5V (which is also RAW for ...
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1answer
67 views

Darlington Transistor \$ A_I , A_V \$

For a darlington configuration: $$h_{ie}=1k,h_{fe}=\beta=50,h_{oe}=25 \times 10^{-6},h_{re}=0 \quad for \quad both \quad transistors,R_L=3k.$$ how can we find the current and voltage gain? My ...
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1answer
416 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 ...
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1answer
40 views

What is this UP 4B2 smd chip in dfn8 case?

Acts probably as a driver to power the motor. There a two of this kind on the board. One burned, the train drives only in one direction.
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1answer
2k 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 ...
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2answers
347 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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2answers
427 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 ...
4
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1answer
400 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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2answers
149 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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1answer
489 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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0answers
70 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
208 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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1answer
215 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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2answers
463 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 ...
6
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4answers
1k 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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1answer
336 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
642 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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2answers
320 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
457 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 ...