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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41 views

Use of clamp diode in ULN2003A

I'm planning to use a ULN2003A 7-channel Darlington driver (datasheet) to control 4 to 7 LEDs in common-anode configuration from a Teensy MCU: (The "trident" is a common-anode RGB LED). The ...
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56 views

Best power transistor for a high PWM output from ESP32

I need your advice whether to use a Tip122 Darlington transistor or a BD137 medium-power transistor Or a IRL3705 MOSFET to drive 10 Parallel infrared LEDs. Each LED has a forward voltage of almost 1.2-...
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38 views

AM circuit LTspice

I have to analyze the following circuit and understand its function. As far as I understand the top part is the simple phase-shift oscillator generating output sine wave at circa 145kHz. The NE555 is ...
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111 views

How to drive high voltage transistor with low voltage op amp?

I'm trying to drive a darlington pair with 24 V collector voltage with an low voltage op amp. I tried adding a PNP transistor so the op amp just have to drive that single transistor, but haven't had ...
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39 views

ULN2803 behavior when its output is not connected to any load in this circuit?

I'm studying the a circuit that is using a driver ULN2803 datashet. The driver is needed for external loads as LEDs when a pin is writing. The situation that I would like to talk about is when the pin ...
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191 views

How does my breadboard circuit diagram look? Am I going to explode myself?

I'm working on my first Arduino project and I thought I picked something simple enough. But before I set my breadboard on fire or ruin any of my components, I wanted to make sure my plan made since ...
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1answer
47 views

Explanation for parallel darlington behavior

I've built and simulated the circuit below in real life, LTSpice and Stack-Echange-Spice. It behaves in a similar fashion in all of these Environments. When the "LAMP2" load is disconnected, the Base ...
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50 views

Darlington transistors killing the output

I was trying to recreate a subwoofer following this website. And the first 2 stages function as expected. The low pass filter is working which i verified , and the the second stage amplifies the peak ...
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1answer
42 views

How do these phototransistors circuits work?

In the figure 1, When there is insufficient light, the darlington transistor is biased on, keeping the relay energized. When there is sufficient light, phototransistor FT turns on; I imagine this ...
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33 views

Convert 8 bit Parallel output from ULN2003 to serial without any Microcontroller

I am hobbyist only with some basic idea about electronics.. I am trying to measure rooftop watertank water level and to display it on a small led bargraph. So by googling I thought about to proceed ...
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1answer
55 views

Multisim vs LTspice : Different Result

I was using the simple darlington circuit below as the test circuit. DC operating point analysis was run on both LTspice and Multisim, with V2 as the manipulating variable and the base voltage of Q2 ...
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1answer
54 views

Input impedance for a darlington pair

I want to calculate the input impedance when I am using a Darlington pair and I'm getting a little confused on the appropriate equation to use. In Electronic Devices by Floyd he gives and example of ...
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44 views

Darlington transistor heats up : regulating transformer output

I am in great need of a 12v DC transformer. So I built one using some components I have lying around: the case of the transformer I have says ...
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1answer
94 views

What advantages does the Darlington pair have over the Sziklai pair?

With all the free time I've had lately due to current events, I've found myself looking into analog amplifier design and analysis (if it helps provide context, my area of expertise is power ...
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62 views

How fast will a resistor heat up under high power?

I am building a circuit for some induction coils on a coilgun, and it will draw about 1.75A from a 12V power source (I know it probably won't be very powerful, but it is difficult to find resistors ...
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74 views

Biasing a emitter follower darlington configuration

Below picture is a simple voltage regulator(link to simulator): The current at the op amps output is at nA region(why?), how can I increase the current at the op amps output without adding a third ...
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4answers
45 views

Determine if a heatsink is required (Darlington TIP120)

I'm planning to switch 1A load at 5V with a TIP120. Looking at it's power derating graph I see that at 5W case can be around 140C, but how can I tell if it will get hotter than that? In the ...
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89 views

Way to show that the current through a Darlington pair is determined by the emitter resistor

I have the following circuit: simulate this circuit – Schematic created using CircuitLab Is there a way to show that the current through \$\text{R}_1\$ is given by \$\text{V}_\text{i}/\text{R}...
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58 views

Requirement of ULN2003 IC in circuit

I'm just a hobbyist and actually from software side. Trying to build a simple water level indicator and found the following circuit using the IC ULN2003. But due to my very less knowledge I'm not ...
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81 views

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
94 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
181 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 ...
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1answer
568 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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306 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
118 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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108 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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37 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
135 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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84 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
54 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
121 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
151 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
48 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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70 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
387 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
936 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
235 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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142 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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298 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
119 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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153 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
77 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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121 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
157 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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234 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
645 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
195 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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1answer
83 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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175 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
153 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 ...