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Questions tagged [npn]

A type of bipolar transistor comprised of n-type semiconductor in contact with p-type semiconductor which in turn is in contact with a n-type semiconductor -> thus NPN. The transistor has three terminals, the Emitter, Base and the Collector. Current injected into the base controls the flow of current from Emitter to Collector enabling amplification and switching.

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How to set fixed bias on transistor 2N2222 for certain specifications?

I'd like to ask how to set fixed bias for this transistor.. It doesn't seem to be working. If anyone know how to calculate it, please tell me. I wanna adjust two resistor values so that Uce = 5,44V, ...
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555 timer circuit switching automotive solenoid with PNP & NPN switching transistors

I am trying to design a 30 second timer circuit to switch an automotive solenoid that draws about 0.8 amps, and need some help please. StackExchange posts have been very very helpful so far, and by ...
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BJT common collector amplifier with a voltage gain sligthly higher than one

How could I explain why a common collector amplifier has a voltage gain higher than one ? In a lab session, I built this circuit : With Vg=30 mVpp and Vcc=15V, students were asked to give the voltage ...
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How to configure NPN transistor as switch and adjust current flow?

Consider the following circuit: As signal a 100 kHz square wave (between 0 and 5 volts) generated by an Arduino. I want to control the transistor so it will let the current from the supply pass ...
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41 views

What to do when you don't find an electric component in Proteus?

I am looking for this component: KSC1815. It is a NPN Epitaxial Silicon Transistor The datasheet is here: http://www.futurlec.com/Transistors/C1815.shtml But when I try to pick that component in ...
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44 views

Base of transistor HIGH without input [duplicate]

I'm having trouble with a simple AND gate, using two 2N2222 NPN transistors: For some reason, the base of the second transistor is high at 2.9V and I don't know what's causing this. I have verified ...
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69 views

Replacing NPN Transistors that failed with similar/better?

I have done some research about this before hand(https://www.electronics-notes.com/articles/electronic_components/transistor/choosing-replacements-transistors.php). I have a switching 12v dc power ...
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Controlling 12V Magnetic Latch Solenoid with RaspberryPi 3b

As the title says I am trying to control a solenoid with a raspberry pi. I am currently using an npn transistor (will post link with parts at the bottom) however I am having a hard time getting it to ...
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Confusion with 555 transistor relay driver

This is probably schoolboy stuff, but before I construct it ... A 555 will output almost the supply rail, or down to zero. A transistor attached to that, with a relay on collector can drive a 12v ...
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76 views

In an NPN transistor, why doesn't current flow without applying a base voltage?

In an NPN transistor, why isn't a typical C-E voltage sufficient to overcome the internal resistance of NPN junction directly? Since we only need 0.7V to overcome the PN junction from the Base to ...
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How does this BJT affect the circuit? If it does, how should I simulate on Circuitlab to see the effect?

I am trying to understand how NPN Q23 in the picture below affects the operation of the left circuit. If it doesn't then what we get is the circuit on the right with the only transistor now being Q30....
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Find voltage across load resistor

Here the zener voltage of the zener diode is 3.3V and base to emitter voltage drop is 0.7V. What is the voltage across the load resistor and how to find it?
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Voltage Circuit Switch with BJT

I have Found One Circuit Which acts as Switch to Pass 15NV (15 Negative Voltage) to Opamps Negative (-VCC) Supply But I am unable to understand its working . Why Two NPN are used in this Circuit ? ...
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DC current gain in complementary transistors

In Class-B amplifiers complementary PNP-NPN transistors are used, e.g. TIP2955 and TIP3055. https://www.electronics-tutorials.ws/transistor/tran_3.html says that They both have a DC current gain, ...
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Off load voltage in npn transistor as a switch

There is transistor tutorial on sparkfun.com (https://learn.sparkfun.com/tutorials/transistors/all). I am wondering why there is 1.3 V drop depicted across the LED1 on the picture, since when the base ...
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70 views

What is function of the resistor in series with bypass capacitor in npn transistor amplifier?

I am new to electronics and recently I was learning about npn transistor as an amplifier. I tried to build one in ltspice XVII. This is my circuit diagram: but the output was not as expected as ...
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79 views

Output current in collector of BC107

I am working on following circuit involving BC107 NPN Philips TO-92 transistor and voltage source of 4.2 V. simulate this circuit – Schematic created using CircuitLab I got some confusion when ...
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PNP and NPN transistor characteristics for this project (see link inside for schematic)

I'm working on this project https://github.com/diyhue/Devices/tree/master/HueDimmerSwitch I would ask which characteristics I need to keep in consideration to choose that two NPN and PNP ...
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Switch resistor with n-channel MOSFET not working

So I try to amplify a photodiode signal with an operational amplifier. As I want to amplify two signals (1 for a high-intensity light and 1 for a low-intensity light) I sort of need to design a ...
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Why is Ic constant in the plot of Vce vs Ic in a common emitter NPN transistor (in active region)?

In this plot, when \$V_{ce}\$ increases in the active region, shouldn't \$I_c\$ also increase as more electrons are getting diffused into the collector? Then, why is it that for a large range of \$V_{...
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50 views

2-stage BJT CC-EC amplifier [closed]

Using proteus I designed this amplifier: But I got this result: I don't know what is the problem in my design. I've been changing the values of the linking capacitors but didn't get any result.
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Need help with three-stage transistor amplifier in LTSpice

I am currently attempting to design an amplifier in LTSpice for an E1 project. My professor tends to emphasize analysis of these circuits, so he hasn't really given us any kind of a design process to ...
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Which region is the transistor operating at?

PNP and NPN transistors in the circuit have identical Is values. Based on the PNP transistor is connected to a DC voltage source. k = 1.38064852×10-23 J/K qe = 1.60217662 ×10-19 C Is = 0.69 fA at 17°...
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87 views

Brake DC MOTOR circuit

I have a DC motor that is controlled with an npn transistor with pwm. Everything works fine. I want to brake the motor instantly. I tried to short the terminals with another pairs of transistors but ...
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Transistors why do they amplify current?

Ok guys I can't understand a thing of the Transistor here is the scheme: My teacher said that when I put 0,7V on the base the PN junction between Base and Collector is direct polarized so the whole ...
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59 views

Need help understanding PNP Base into NPN Collecter circuit for LED Array

I am a novice in circuitry and I'm trying to make an 8x8x8 LED Cube using an instructables guide for a school project. I have ordered all the parts and was testing the grounding circuit for each layer ...
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40 views

Is resistor needed to drive NPN Transistor from EEPROM

I am using this EEPROM in read mode: http://ww1.microchip.com/downloads/en/DeviceDoc/doc0270.pdf And am using this transistor: https://www.onsemi.com/pub/Collateral/P2N2222A-D.PDF I need my EEPROM I/...
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168 views

Arduino - Using NPN transistor as a switch to pull-up/down analog pin

Let me start by saying that I am not an EE, and my knowledge in Electronics is basic, so please bear with me and be patient if, initially I am bending a few rules. In Epee fencing, a touch is awarded ...
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85 views

Driving LED with 555 timer and BC639 transistor

I am trying to produce an LED dimmer circuit using a 555 timer circuit and a BC639 NPN transistor. I know there are better transistors that would suit the task better, but the BC639 is what I have to ...
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1answer
74 views

Current spikes on rising and falling edge of NPN BJT switch

I am simulating a simple NPN BJT switch for PWM in LTspice, and I observe some current transients on the rising and falling edges that I do not understand. The circuit is here: Picture of the falling ...
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82 views

NPN transistor numerical

I think the steps will be STEP-1: \$V_x - V_{BE} = I_B\times R_E\$ STEP-2: \$I_B = I_{ra} - I_{rb}\$ STEP-3: \$V_x = V_{in}\times R_B/(R_B+R_A)\$ Please tell me i am correct or not??
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For MMBT2222; How to get hfe value to calcluate minimum base current to drive transistor in Saturation?

If my collector current VCC = 3.3V & Ic = 31.82uA then how to calculate minimum base current is required put transistor in saturation mode? Depending on it I will calculate base series resistor ...
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45 views

Over-current sense

I am using a circuit shown below. it is designed to sense 1.5 A whenever the load takes current >= 1.5 A. Rsen senses the related voltage and activates the transistor. Here I use a Rsen = 0.46 R(0.7V/...
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56 views

MMBT2222 Datasheet doesn't mention maximum base current. How to calculate it?

The MMBT2222 Datasheet doesn't mention the maximum base current. How to calculate it? So that design should not exceed it. I want to use it for switching in common emitter configuration; where the ...
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54 views

Making a DC motor turn in saturation and cutoff modes of an NPN transistor

simulate this circuit – Schematic created using CircuitLab So I have a DC motor that should turn with light on LDR and should stop when I cover LDR or turn off the lights. Basically the ...
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Non-inverting output of transistor circuit (at NPN base) is 0.69V max. why?

I tried to make a simple NPN transistor inverter so that I can use the strobe line of the parallel port to store data in two separate flip-flop IC's. (74HC174 and 74HC574) The IC that data will be ...
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122 views

Can someone explain how I turned on a circuit by touching it?

I was just trying to learn how a transistor actually works by tinkering around myself. I have an Arduino running a flashing light program. I hooked up an NPN transistor to test out how I can make it ...
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66 views

Reduce active region of NPN transistor

I've got a small LED garden lamp, battery operated, that turns on with a switch. I am currently trying to use a photoresistor that I have to make it turn on when it gets dark (so I don't have to ...
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64 views

Can I use an NPN BJT transisor as a standard switch?

Is is possible to use a NPN transistor as a normal switch? If I put 5 V on the transistor base the switch is closed and if there is 0 V on the base the switch is open. Does the transistor need to ...
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Calculating collector current of NPN BJT with LED & resistor

I've been trying to wrap my head around the current I measured through the collector branch vs. the expected calculation for collector current and believe I have a knowledge gap in what to do. The ...
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1answer
59 views

NPN BJT Transistor Circuit Analysis Problem: Is This Question Solvable?

I've been doing some circuit analysis questions as practice but came across one that seemed very odd: As far as I can tell, this question is missing information and therefore unsolvable? I was able ...
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63 views

Transistor Reverse Biasing - AC

I am working on a project which require to activate a 24V Rated relay using a 3.3V rated IO. To provide adequate isolation I have added a Opto-isolater stage. In order to increase the current output ...
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3answers
144 views

NPN transistor as switch (actual voltage readings)

I started learning Transistors with this tutorial from the Sparkfun website. The tutorial is good and pretty easy to understand. So I decided to put my learning to the test and assembled a simple NPN ...
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1answer
75 views

Why doesn't current flow in the other loop?

I am just now learning about how transistors work, so please let me know if I have a misunderstanding. I ran a simulation of the circuit drawn below, and the results were that current flowed only in ...
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Test a transistor with a multimeter

I used the guide at https://vetco.net/blog/test-a-transistor-with-a-multimeter/2017-05-04-12-25-37-07 to test a transistor with my DMM. The NPN transistor I used to test is the "mospec tip130 No11D" ...
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102 views

What is the function of this npn transistor?

I see that the R306 resistor is trying to limit current when the npn transistor is on. I am not sure what the resistance offered by the npn is but it looks like the current through the 47k resistor ...
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113 views

Operation of BJT with low values of Vbe (“cutoff” region)

Many sources claim that when the base-emitter voltage becomes smaller than approximately 0.6V-0.7V, the bipolar junction transistor goes in the cutoff region and there is zero base and collector ...
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98 views

Command Solid State Relay using NPN transistor 2N2222 [duplicate]

I'm trying to command a Solid State Relay with the HV1 pin, I can't connect it directly(HV1 to CH1) due to the fact that the impedance on that pin is too low and I only obtain 2.8V when connected. So,...
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Voltage controlled switch simulation

I'm trying to short two pins on a chip when an audio signal is received and float them otherwise (same effect as a tactile switch). I thought the best way would be to use a voltage peak holder and a ...
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2answers
160 views

Prevent NPN Transistor Base-Emitter Current

I'm making a simple AND gate array out of 2n2222 transistors. Here is one cell: simulate this circuit – Schematic created using CircuitLab When Input "A", is disabled, and "B" is still on: ...