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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4answers
72 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 ...
0
votes
1answer
114 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 ...
0
votes
1answer
59 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
64 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 ...
0
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1answer
67 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 ...
1
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1answer
111 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 ...
0
votes
1answer
50 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 ...
-3
votes
2answers
64 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 ...
1
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2answers
160 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 ...
1
vote
1answer
85 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
votes
1answer
55 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 ...
1
vote
3answers
73 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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votes
2answers
110 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 ...
0
votes
0answers
68 views

NPN with Arduino setup correct

I created a music visualization (code and circuit) with Arduino and LED-Stripts. I uploaded it to GitHub. The circuit works, but the wiring especially of the NPN Transistors seems a little odd: ...
3
votes
2answers
228 views

Understanding a 2 transistor oscillator?

I asked a question here about why I was getting a sawtooth wave from a two transistor oscillator. While that question is answered, I don't understand how the circuit produces oscillation in the first ...
1
vote
1answer
136 views

2 NPN Transistor Square Wave Oscillator?

I have built the circuit found here. I substituted with 22K resistors at R2 and R3, and substituted C1 and C2 with .022uF capacitors. These are all the components I have lying around. Everything ...
1
vote
2answers
163 views

Using PNP instead of NPN merely requires one to make circuit upside down and reverse current direction, why do we not just use one of the two types?

Using PNP instead of NPN merely requires one to make circuit upside down and reverse current direction, if this is true then why don't we just do everything with NPN transistors? Are there any ...
1
vote
1answer
57 views

e13007f npn transistor datasheet reading for turn on time

I am reading datasheet for e13007. You can get it here: http://www.datasheet-pdf.com/datasheetdownload.php?id=520587 (click on "Download PDF for PC") In "Electrical Characteristics" section under ...
1
vote
2answers
58 views

Magnetic pulser circuit

I am trying to recreate this device from: The housing 14 is shown with a control panel 16 for purposes of illustration. In one embodiment of this invention, the control panel 16 includes only an ...
0
votes
1answer
76 views

Can I use serial communication for audio amplifier remote turn on?

I have a cheap Chinese tablet/GPS/dash-cam in my car. The problem is that I can't hear driving instructions on GPS as the volume is too low. I don't want any external wires for additional speakers and ...
0
votes
4answers
81 views

Is the hfe of a transistor dependent on the resistance on the other parts of the circuit?

I have a circuit using a NPN transistor with a motor before it and a pwm into the base. The motors draws a current of 600mA if I plug it directly into the power source, just under the maximum allowed ...
0
votes
2answers
66 views

What resistors should I use?

I have just started learning the basics of electronics. I found a circuit which uses NPN as signal Amplifier and powered by 12V source. The signal source is a audio from Mobile headphone jack. I ...
0
votes
4answers
109 views

Optimize PNP/Diode Schematic

I am trying to design a circuit which has four switches, numbered 1-4 as in the diagram. The circuit should function such that closing switch n turns on light ...
5
votes
1answer
405 views

How protective diode protects transistor from breakdown?

Please, explain the process of breakdown; how exactly this protective diode protects the transistor? In a Horowitz & Hill book, "The Art of Electronics", 2nd edition, in "Chapter 2 - Transistors" ...
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votes
1answer
60 views

NPN BJT used for DC Switching Load [closed]

I am trying to learn some things for a class. This is not homework, just studying for an exma. It has to with calculating values when using a NPN BJT. I have five (only three because other 2 were not ...
2
votes
2answers
288 views

What (if any) is the leakage current through a NPN (C-E)?

So I have a circuit where I need the current consumption to be low. Therefore I am using a 10M\$\Omega\$ resistor to 'pull-up' the pin on a chip which will need to be switched between high and ground ...
0
votes
0answers
105 views

Voltage divider biasing circuit switch, which resistors should I use?

Goal: To turn on (open) a solenoid valve valve for irrigation when the soil moisture sensor reports a value below X% and shut it off (close) above X%. X should be able to be changed between say 20-80% ...
0
votes
0answers
75 views

Do we ever need to use multimeter's transistor current gain measurement feature?

Many cheap multimeter have this feature that they can measure the hfe of a NPN or PNP transistor. Does anyone ever need to use it? I mean, when we design something using discrete transistors, we look ...
0
votes
1answer
52 views

HIGH speed Level Shifting

I was working on FPGA project that will be able to detect and timestamp input pulses from a series of detectors giving off a 20 ns pulse for each positive detection. Problem arises is two fold: the ...
0
votes
1answer
228 views

NOT gate with an NPN (2N3904) transistor not working?

I have the book Getting Started In Electronics, by Forrest M. Mims III, and it has an RTL NOT gate schematic that looks pretty much the same as this: About a month or two ago, I was starting to get ...
1
vote
3answers
203 views

LED with a transistor on each side

I'm trying to make a circuit with a transistor on each side of an LED so it only lights up when both transistors are activated. The transistors need to be on either side of the LED because the LED ...
0
votes
1answer
64 views

Darlington does not switch

I have a darlington Transistor circuit. Like in the schematic i attached. When i power up the 3V3 from my raspberry, the led is not on. When Doing Danke same with 12v instead of 5v, it Works ...
-1
votes
1answer
79 views

Conceptually problem with n-p-n transistor

Suppose it has 3 leads (let A,B,C) and I connect B and C by moist fingers and A to the positive lead of an ammeter and C to the negative lead of the ammeter,I find a large deflection.Then A,B and C ...
1
vote
3answers
94 views

How do I find the input impedance a common emitter amplifier?

How do I find the input impedance of this common emitter amplifier? \$V_{CC}\$ is supposed to be at the top of \$R_5\$. I forgot how to do the analysis to find the input impedance. The input goes ...
0
votes
3answers
169 views

Need help understanding Transformerless Push-Pull transistor circuits

I am new to electronics and I am currently trying to learn a little more about how NPN and PNP transistors work. While doing some research, I stumbled across a circuit design called the ...
-1
votes
1answer
75 views

Control LCD with TIP121 on Arduino not displaying anything

I'm trying to control the power of an LCD I2C display. My project uses and Arduino and LCD, but when Arduino goes to sleep, the LCD stays on. So, to solve this problem, I connected a TIP121 transistor ...
1
vote
2answers
180 views

Would this circuit work? NPN & PNP transistors ~in parallel:

Want to make a thing to test for both NPN and PNP transistors (using RPi GPIO power) and have sketched a diagram. Can you use both NPN and PNP resistors in parallel like this? Could this circuit ...
0
votes
0answers
46 views

Power feeder current and LTSpice simulation

I'm trying to develop a power feeder as already state in question Power feeder scheme adaptation. I have done some adjustments, now my circuit is The voltage regulator is an LM317. Since I have to ...
1
vote
1answer
78 views

using transistor to switch 3v from 2

i need to use a GPIO pin to test whether an LED is on/off. the LED only has 2v power which is not enough for my digital input (3.3v) so i would like to use a transistor to amplify the voltage from 2v ...
0
votes
3answers
134 views

(Beginner) Type of (NPN?) transistor to use for RasPi

I'm new to EE. I burned out a Raspberry Pi by running an electric motor directly from its GPIO pins, and then I learned about transistors. I now have another RasPi, but I'm not sure what transistors ...
1
vote
2answers
223 views

Amplify speaker with 9v battery and one transistor

I started electronics recently and I'm trying to make the most basic mp3 amplifier. I try to amplify the music from my phone to the speaker. My phone already amplifies the sound when I connect it ...
1
vote
2answers
146 views

NPN vs PNP Transistor Wiring

Whilst reading about differences between PNP and NPN transistors I came across the following circuit diagrams: ...
0
votes
1answer
135 views

Transistor switch logic, multiple lines

I have the following problem that I need your help solving. I have two digital input signals, let's call them D1 and D2, they are 0-5V, and max available current is 20 mA, and two output signals, ...
1
vote
3answers
138 views

Help with simple Arduino/Transistor/Solenoid circuit

I'm trying to use an Arduino+transistor to control a shutter (which I believe is a solenoid) at work. The shutter is normally connected to a power supply by two small wires (positive and negative) and ...
1
vote
3answers
185 views

NPN “Saturation” Mode and switching

So, one thing I've been reading about is Sparkfun's tutorial on transistors,focusing on BJT (specifically NPN, but a bit into PNP). I'm super new to transistors and such, so please bear with me. ...
-1
votes
1answer
105 views

NPN switch: What is wrong with this circuit?

I'm trying to use a single source for both output and an NPN switch (5V - 2Amp). I cannot get higher than 500mA at the output, with VLoad about 4.3 V max. simulate this circuit – ...
0
votes
1answer
48 views

Incompatibility between 5v processor and 12v source

L,H on the diagram below represent processor pins in LOW/HIGH states. LOW is 0v, HIGH -- 5V. Difference in voltage levels (5V vs 12V) leads to problems -- current flows on paths where it shouldn't. If ...
2
votes
1answer
147 views

Why does the colllector current decrese with decreasing collector-emitter voltage in this circuit?

I'm trying to understand how the circuit below works so I ran a simulation with TINA and I got the curves shown on the right (C3 is already charged). Here is a bigger one Considering the ...
0
votes
1answer
46 views

How to find power displacement in transistor npn?

My circuit has a Vcc of 18v and a Vee of -18 ,Rc 330 ,Ic 20 mA ,Vce 8.58V, Re 470, Rb 5.1k, Just want to know the formula for power dissipation for Rc and within the transistor, Please.
0
votes
1answer
82 views

What is max Vce for a transistor with Ic of 50 mA and without exceeding PD(max) of 1.2 W

What is max Vce for a transistor with Ic of 50 mA and without exceeding PD(max) of 1.2 W?