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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31 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
39 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
69 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
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 ...
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76 views
Darlington pair. Purpose of components
Giving the following schematic:
What is purpose of R1 and the diodes ?
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1answer
28 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 ...
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1answer
62 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
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 ...
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1answer
185 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
73 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
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 ...
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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 ...
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2answers
194 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
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 ...
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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 ...
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4answers
173 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
51 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
299 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
287 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
276 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 ...
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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. (...
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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 ...
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2answers
49 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
64 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
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 ...
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1answer
35 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
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 ...
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2answers
255 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
331 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
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 ...
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2answers
116 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
381 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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65 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
163 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
174 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
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 ...
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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 ...
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1answer
261 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
565 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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971 views
How to test darlington transistor in-circuit?
I'm trying to diagnose a faulty current limiting circuit in a piece of lab equipment from back in the 80s. The fault is too much current.
The tail end of the circuit is below. Q3 represents a ...
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2answers
259 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
362 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
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 ...
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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
600 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
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, ...
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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
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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 ...
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0answers
200 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
3k 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, ...
