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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.

4
votes
2answers
390 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 ...
1
vote
2answers
88 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"...
0
votes
3answers
61 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 ...
0
votes
1answer
50 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
votes
1answer
593 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, ...
2
votes
1answer
58 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 ...
0
votes
2answers
136 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 ...
0
votes
0answers
46 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 ...
0
votes
1answer
45 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 ...
0
votes
2answers
265 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....
0
votes
0answers
79 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 ...
0
votes
1answer
184 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 ...
0
votes
1answer
277 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 ...
0
votes
1answer
342 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 ...
1
vote
1answer
74 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 ...
0
votes
0answers
90 views

Darlington pair. Purpose of components

Giving the following schematic: What is purpose of R1 and the diodes ?
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
1answer
33 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
vote
1answer
68 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 ...
2
votes
2answers
134 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 ...
1
vote
1answer
212 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 ...
0
votes
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 ...
1
vote
2answers
109 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
3answers
113 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
2answers
232 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 ...
2
votes
3answers
672 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 ...
1
vote
2answers
3k views

Is it possible to use a ULN2003A Darlinghton array instead of multiple TIP120 transistors?

Looking at the datasheets, I'm not sure their specifics match; TIP127 and ULN2003A My intention is to do something like this, but with the ULN2003A, that I have already: The reason why is that I ...
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-...
0
votes
4answers
208 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 ...
0
votes
1answer
65 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 ...
0
votes
1answer
56 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 ...
0
votes
3answers
325 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 ...
0
votes
2answers
338 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 ...
0
votes
2answers
57 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 ...
2
votes
1answer
76 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. (...
1
vote
1answer
355 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 ...
8
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 ...
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 ...
0
votes
1answer
39 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.
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 ...
0
votes
2answers
308 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....
0
votes
2answers
383 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
votes
1answer
366 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 ...
6
votes
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 ...
-1
votes
1answer
448 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 ...
0
votes
0answers
68 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 ...
0
votes
1answer
194 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 ...
1
vote
2answers
399 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 ...
0
votes
1answer
291 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 ...
0
votes
1answer
581 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}{...