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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ULN2803 relay driver working for high loads
I am trying to understand the working of this Darlington transistor array. I am using it for inductive loads and for driving the loads of my relays, but now I am trying to understand the part of its ...
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1answer
57 views
Why are there three transistor pairs in Class B Power Amplifier circuit?
I have a Class B amplifier circuit to be done in lab. Why three pair of transistors are used in this? I suppose one is a Darlington pair but what is the requirement of the third one. Also, why there ...
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4answers
132 views
What's wrong with this PWM-controlled constant current sink?
T10 gets very hot and starts melting within 30s, even with a heat sink and values way below its rated 15A.
Edit:
I know it is not a true PWM controlled constant current, but that what I can do with ...
3
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1answer
488 views
Current mirror: is there a name for this NPN-PNP pair, and how does it work?
I'm looking at the schematic for the MC1460 voltage regulator. At the top it has three current mirrors, each with an NPN-PNP pair. Is there a name for that transistor structure? These pairs look like ...
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3answers
103 views
Darlington as CB
Why do we use Darlington pair?
I've heard that we don't use it as common base. Why is that?
Why don't we just develop a BJT with high beta value istead of using this structure?
What are the different ...
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4answers
84 views
What is an open collector?
I am new to electronics, and I'm reading a book on embedded systems and bumped into an "Open Collector". I know that a transistor has a base, which acts like a switch for the current to flow from ...
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1answer
75 views
DC analysis of Darlington pair
So I'm having this darlington pair here
I'm doing DC analysis of this darlington pair
Can anyone explain why is R2 is 6.58, shouldn't it be aprx 7.39?
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26 views
Small Signal model of darlington pair with resistor
Im trying to create a small signal model of a circuit with a darlington pair in it. The circuit is the one in the image below.
I have managed to do this small-signal model but i feel it is a little ...
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1answer
111 views
How does a darlington pair work?
How does a darlington pair work?
I am curious about how the second transistor sustains the current Ie of the first transistor.
Why is the base not damaged despite ...
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62 views
Is it necessary to opto-isolate a darlington array output?
I've got the following circuit going:
A Vishay opto-isolator (CNY74-4) that takes input from buttons that work on 24V, and outputs to microcontroller pins (an Olimex ESP32-PoE-ISO in my case).
A ...
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1answer
46 views
How must be the pull up resistor circuit connected to the driver input?
I have this circuit for getting 12V or 0V from external control signals. Signals will arrive by pin connector to my board. Switches will also be out of this board.
External control signal could be ...
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3answers
112 views
Output stage using 2 transistors
I want to understand how does this 2-transistor circuit work. It is used in a schematic for increasing the current rating at the discrete output stage. This does not look like a standard darlington ...
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3answers
98 views
Darlington array: How to output desired voltage at uln2803a driver colectors?
Someone suggested this driver array to get the current I need:
datasheet
I also need a 12V signal and about a current of 100mA in order to control a relay coil. My 12V signal would come from a logic ...
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1answer
44 views
Multiple Lamp indicators and LED driving using TPL7407LA simultaneously
I am using TPL7407LA for driver circuit, it will be getting inputs from pic18f67k40 and driving multiple Lamp indicators(24v) and multiple LED indicators(12v).
My question is : Is it possible to ...
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1answer
62 views
Determine total current in a darlington transistor
I'm trying to figure out what will be the total current consumption of a TIP120.
Looking at the internal schematic I see that the second BJT's base is following the emitter of the first one so it ...
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3answers
325 views
ULQ2003 not driving a Relay properly
I am driving a 9V DC (5 PINS) Relay from darlington array ULQ2003.
The ULQ2003 COM pin is connected to 9V power supply while the Relay coil is connected to +12V supply. The Ground of both are ...
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1answer
752 views
What is this triple-transistor arrangement called?
For an old Fuji 2DI200D-100 power transistor module, it uses three transistors internally for each half-bridge:
The circuit in question doesn't connect to the middle bases at all, just B1 and B2, so ...
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2answers
187 views
Complementary transistor pair with a bipolar transistor and a MOSFET
I own a set of Soviet IN-14 Nixie tubes and I would like to use them to make a vintage clock. I found this example schematic of a "Nixie clock":
I don't understand what is the purpose of using a ...
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2answers
123 views
Why it is said that second transistor cannot enter saturation mode in Darlington pair?
When I made equations it came out that for both of transistors to be in saturation
Vc-Ve2<.2V
Vc-(Vb2-.7V)<.2V
Vc-Vb2<-.5V ............{eqn a}
As for first transistor to be in ...
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0answers
125 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
65 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
145 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
56 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
94 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
133 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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2answers
175 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 ...
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1answer
629 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
135 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
125 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
59 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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136 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
134 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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157 views
Darlington pair. Purpose of components
Giving the following schematic:
What is purpose of R1 and the diodes ?
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1answer
54 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
109 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
156 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
759 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
124 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
147 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
209 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
629 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
809 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
344 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
365 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
116 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
469 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
446 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
530 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
108 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
288 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 ...
