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 ...

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Comparing sensitivity to temperature changes of BJT (transistor) circuits in Common Emitter Configuration

I measured Ic variation with Ib when Vce = 15v kept constant for BJT (NPN) in Common Emitter config and also BJT Common Emitter config with series 47 Ohm resistor connected. I cannot explain why the ...
5
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3answers
599 views

What does reverse diode on NPN symbol indicate?

I've been scavenging parts from compact fluorescent (CFL) bulb ballasts just for the sheer joy of getting something for free. Plus, I'm all into inductors just now and there are some nice little ...
2
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1answer
67 views

what is the collector gain of a transistor?

I was wondering what exactly collector gain is for npn transistors, or more specifically if there is some sort of equation for getting it, and if its value changes as you change the input ...
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1answer
29 views

V CE in the emitter follower configuration

Is it true that voltage between collector and emitter is 0 in the emitter follower configuration? (We intentionally use the saturation region of the transistor)?
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1answer
95 views

PNP to NPN Transistor switch

I'm working on project that requires I switch a 12v power supply on the high side of a circuit, using a 3.3v micro controller. To make this work, I'm thinking a can connect a PNP transistor on the ...
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1answer
71 views

about semiconductors

I have got the following doubt. Hope you clarify it. Thanks in advance electron when finishes its life time recombines with hole in valence band . its given that in an pnp transistor holes of emitter ...
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70 views

Transistor with emitter attached to another transistor's base

I made a circuit that looks something like this: simulate this circuit – Schematic created using CircuitLab If I touch the loose wire with my finger, the LED will light up. Could someone ...
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1answer
69 views

BEC or CEB NPN Transistor [closed]

I am looking for a small, inexpensive NPN transistor, similar to 2N4401 in specs, with a BEC or CEB pinout. Does anyone know of any?
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1answer
46 views

Forced beta too small

Let's take an example in which the recommended beta for a transistor's(NPN) saturation is 10.If you use a forced beta smaller than 10,will the transistor still be saturated succesfully?Can hFE be ...
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1answer
41 views

Help to calculate the collector current

Above circuit is taken from a book. It uses an NPN and a PNP transistor combination. In saturation, the author's answer to the Q2's collector current is 4.4mA and claims only 0.6mA of it comes from ...
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76 views

A confusion on the current gain of an NPN transistor

In above screenshot V2 is increasing ramp voltage from 0 to 12V, which accordingly increases Ib. Transistor is an NPN type. Ic(q1) is the collector current. Vce = V1 is a constant 1V. So it means ...
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2answers
80 views

No plot for DC current gain in datasheet

Here is the data-sheet: https://www.fairchildsemi.com/datasheets/2N/2N4401.pdf I want to use a 2N4401 NPN transistor in active region for amplification, and I want to know its beta(DC current gain) ...
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3answers
130 views

Vce too high. Help?

I have been working on a high-powered LED light bar. The design powers them almost directly from the mains, but limits current using a 555 and beefier NPN. Below is a simplified schematic. Obviously ...
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1answer
340 views

Why am I getting negative base current in LTSpice simulation?

When I was trying to bias an NPN transistor I noticed that the base current Ib is negative in LTSpice. So for the sake of simplicity I only apply voltage to the base-emitter junction. As you see in ...
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1answer
85 views

BJT transistors AND gate

I am trying to build a simple AND gate using 2 2N2222 transistors and the +5V source from an Arduino board. At first I tried the circuit without the R1 and R2 resistors but the output was 1 when B was ...
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4answers
90 views

Using NPN-Transistor as switch not working

I have following schematic: simulate this circuit – Schematic created using CircuitLab But the motor is not working, the NPN-Transistor does not seem to let any current through. What am ...
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1answer
196 views

How to send out 60khz signal from antenna?

BACKGROUND In Japan there are radio-controlled clocks. Time is synchronized by 40khz (in west Japan) and 60khz (in east Japan) radio, which is broadcast from transmission towers. The signal is known ...
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1answer
114 views

Finding “beta” in an NPN transistor

I am trying to figure out "beta" value of an NPN transistor, but I am not allowed to measure current directly. (Although I do have access to lab equipment and other components such as multimeters, ...
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1answer
90 views

NPN and PNP Built-in Voltage

Does the base-emitter connected BJT have the same built in voltage as the base collector connected BJT? Why or why not?
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1answer
84 views

What is the purpose of this transistor in an Apple Time Capsule?

While taking apart a 2009 Apple Time Capsule, I found a 2N3904 NPN transistor on a 2-wire cable with the emitter connected to one wire and the base and collector connected together and to the other ...
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1answer
54 views

Is this NPN transistor AND logic gate practical?

Most places on the internet that I see give a schematic for an AND gate that is something like this: simulate this circuit – Schematic created using CircuitLab The only thing about this ...
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1answer
62 views

How to determine value of Vbe ON in BJT

I have to do a lab report which requires me to know the value of the base emitter voltage of the BJT in the forward active region. Last week in lab I measured a lot of data points for different Ib Ic ...
3
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1answer
131 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 ...
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0answers
49 views

Thoughts about H bridge

I'm planning to build a pwm driven H bridge. I have all set up, flyback diodes, pull up and down resistors on high and low on bridge's side, decoupling capacitors and so on, but I only have TIP122 ...
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35 views

How does this simple 2 NPN, 2 cap, 4 resister flashing circuit work? [duplicate]

I discovered this circuit and I am fascinated at how simple and effective it is. I am also unable to figure out how or why it works. Can some one explain how the is circuit is able to flash? You ...
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1answer
96 views

NPN Transistor; base grounding through emitter

I am using NPN transistors in an H-bridge to connect a DC motor to ground. My problem is the base of the transistor seems to be grounding through the emitter pulling the value of my logic circuit to ...
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1answer
72 views

NPN transistor negative base voltage

In this circuit, when I switch off the transistor opening the switch SW1, a negative Voltage of circa -6.5V appears at its base. I would like to understand why, my first hypotesis is because of the ...
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1answer
74 views

does NPN transistor allow current to flow when applying +ve to base from diff battery?

Please forgive me if this is a stupid question, I am not an electronics student but a software developer trying to understand a transistor behaviour. I just learned about transistor a few minutes ago ...
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1answer
129 views

emitter to base amazing transistor effect

As I'm a beginner I was playing with transistors connecting them parallel, serial, making AND/ OR logic gates and so on. I connected all collectors to + and each transistor emitter to another one's ...
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1answer
108 views

How to drive high current transistor with Arduino?

I need to control a 6 volt 100w watt incandescent bulb with my Arduino. I was thinking of using a TIP35C transistor but I realized the 40mA(max) output of the pins on the Arduino would be inadequate. ...
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3answers
110 views

What's the name of this NPN configuration?

I can't find it anywhere. I know it's not a darlington pair. I tried looking at the 'common emitter' configuration but the explanations of that all talk about a single transistor. The switch on the ...
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2answers
108 views

Uninterrupted current triggering transistor base

I'm still pretty much a electronics-beginner, I'm currently working on modifying a USB game-pad to use switches instead of buttons and I want LEDs to accompany the switches. The basic solution I was ...
3
votes
2answers
90 views

Transistor not triggering

When the base side of the transistor giving a voltage 0 V, across the collector side getting 2.3 V and if give to the base side only voltage 3.0 V, the collector giving voltage 2.9 V. It is not ...
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1answer
56 views

How to delay the transistor turning on using a photoresistor?

I am a beginner in electronics, my project is the following: I am trying to build a simple circuit to switch on and off my garden lights according to the brightness level. More to the point, I'd like ...
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1answer
132 views

Effect of negative voltage at NPN transistor base (interesting example)

I'm trying to understand the behaviour of an NPN transistor and two diodes connected to the output of an instrumentation amplifier [image below]. The transistor appears to switch on when there is a ...
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1answer
54 views

Is this a safe design for an input at a 74HCT165

I'm new to designing my own circuits so please be kind and tell me if I'm right with my thoughts or if I have errors in it. Thanks! The purpose of the 12V is to compensate the resistance of long ...
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1answer
86 views

How to drive NPN transistor based on this circuit?

I just built a fan speed controller, using the following schematic: Now if you connect 12V from 555 and connect pin 7 to the blue CPU fan wire, it controls the speed, but whenever the PWM signal is ...
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4answers
103 views

Read -5V Signal with Microcontroller

I have the following problem. I want to read an -5V Signal using my Microcontroller. I have the following circuit setup, but it does not work. My problem is that the the signal is high while the ...
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1answer
134 views

Transistor inversions

Having some trouble with transistor logic. I have an existing circuit with a 3.3V rail and signal rail that is pulled to 0V when asserted, i.e. active low. I ultimately need to control four 12V LED ...
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1answer
75 views

MOS gain, how much is it, Bipolar as a key

Sorry for the stupid question. Is the MOSFET with current gain or voltage gain? I know it's voltage controlled, but what's the gain from Gate to Drain? And how do I calculate it? I know in key mode ...
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2answers
130 views

Controlling pull-up pins from external circuit

I have a circuit with an Arduino controlling a 2-channel, normal-off, opto-isolated relay board, 5V input signals, turning relay ON when the Arduino digital pin is set LOW. The relays are controlled ...
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1answer
73 views

Transistor active mode

I have been looking on the web but all I found was theory that I couldn't fully understand,nor apply .How can a NPN transistor be switched on in active mode?I would appreciate if you would give a more ...
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1answer
428 views

NPN Transistor For 3 volt base to switch/control 5 volts

I have a 3 volt microcontroller that I want to control the power to a 5v microcontroller. What transistor can use a 3 volt base and allow 5 volts through the emitter/collectors. What type of NPN ...
1
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1answer
200 views

24V proximitiy switch, NPN transistor, Arduino interrupt input

I build circuit which take proximitiy sensor as input to circuit (24V). With this 24V we switch on and off NPN transistor. On the side is Arduino with interrupt enable when pin is LOW. So I need ...
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2answers
84 views

NPN Transistors [duplicate]

How does NPN transistors actually work? In the picture below, I understand that electrons flow in A as the n-p junction of the Emitter and Base is forward-biased. However, the p-n junction of Base and ...
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2answers
223 views

SMD vs THR Transistor for Relay

Designing a Relay control from a MCU's GPIO, there are some requirements to take into account. Coil Voltage: 3V Coil Resistance: [36-45]Ohm Relay Voltage: 250Vac // 30Vcc GPIO Voltage: 3V3 Max GPIO ...
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1answer
249 views

PNP or NPN Transistor for this schematic?

I am quite new to electronics and hoping to build a voltage regulator using the schematic below. I will be using a 7806 regulator and a 7.4 Lipo battery (yes, the schematic is probably a little ...
2
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1answer
151 views

Can I use a NPN Transistor as a Varactor Diode?

I am currently building a crystal controlled AM transmitter. The circuit that I'm using call for a NTE – 613 varactor diode (which will come in a few days). I was wondering if there was an alternative ...
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3answers
333 views

How to avoid Relay buzzing noise? (LDR dependent)

I have the following circuit where I'm switching a relay based on whether it's day or night. I made a voltage divider using a pot and an LDR, which leads to the NPN transistor. So when it's dark the ...
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2answers
304 views

NPN transistor: collector current flowing to emitter without connecting base?

I have a circuit where a LED has its cathode connected to the collector of my C8050 (or SS8050) NPN transistor, with the emitter grounded. Even though the base is left floating, the current is still ...