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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0
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4answers
104 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
370 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" ...
-3
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1answer
51 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
161 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
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0answers
65 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
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0answers
57 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
39 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
103 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
183 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
46 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
57 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
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3answers
82 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
116 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 ...
0
votes
1answer
48 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
122 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
40 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
68 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
93 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
121 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
101 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
104 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
119 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
147 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
98 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
41 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
121 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
44 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
54 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?
0
votes
1answer
123 views

How can I switch power between two hard drives using transistors?

Application I have two hard drives that draw approximately 1.1A / 1.5A on their 12V and 5V power pins. I have several 2SA1020 PNP transistors which are rated 50V 2A and was hoping to use them to ...
1
vote
3answers
132 views

Determine saturation base current from NPN transistor datasheet (or what resistor do I need to ensure saturation?)

The Fairchild 2N3904 has a long data sheet so let's use that for this exercise. I'm interested in using an NPN in common emitter configuration --- it's for switching. It's my understanding that an ...
0
votes
3answers
183 views

NPN Transistors for motor control

I wondered if someone could offer advice here. I have a 3.3v dc motor. Obviously, i can change the direction it turns by flipping the + an - leads round. Can i acheive the same thing but with 2 npn ...
0
votes
1answer
92 views

How collector-base junction in BJT works

I have read some answers about how BJTs work, but I'm still not convinced. To show my doubts better, suppose we extract base and collector from BJT NPN transistor with all its construction details ...
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votes
2answers
128 views

How can i convert an NPN transistor to PNP transistor? [closed]

Could anybody help me by providing a circuit diagram for converting a NPN transistor to a PNP transistor? Thanks in advance
0
votes
1answer
132 views

how to wire NPN to switch DHT22 temperature humidity sensor on arduino [duplicate]

I am using the arduino with DHT22 temperature, humidity sensor, but i don't want to constantly power the sensor, so I would like to have a NPN 2N2222 transistor to control when to the give the power. ...
1
vote
3answers
102 views

NPN Darlington circuit for 12V Diesel Glowplug

I'm trying to build a very simple circuit to drive a glowplug. I am using a TIP122 NPN. simulate this circuit – Schematic created using CircuitLab I wanted 0.017A going through the 12V ...
1
vote
2answers
387 views

Transistors to switch 12V 2A

I need to switch some power to a device, so I was wondering, if this will work OK, or do I need to add some other stuff to protect it, or make it work correctly. I ran some simulations, on ...
1
vote
3answers
185 views

Is controlling a voltage regulator's EN/SHDN terminal directly by 3.3V microcontroller possible?

Let's take the LT1763. The datasheet says that "The SHDN pin can be driven either by 5V logic or open-collector logic with a pull-up resistor." On the other hand the chart "SHDN Pin Threshold ...
6
votes
2answers
140 views

Why the base current decreases automatically?

Given this circuit: simulate this circuit – Schematic created using CircuitLab I don't understand why, when simulating it by increasing parametrially the V2 from 0V to 12V keeping V1 ...
0
votes
1answer
149 views

Unusual voltage drop at BJT (2N2222)

I'm using BJT (NPN) that is supplied with 7V DC signal at the collecter, 5V DC signal at the base and need a 12V output at emitter. Right now i'm getting 4.35V at emitter. How can i implement it?
0
votes
1answer
137 views

How can I create an SCR using a PNP and NPN?

Several times I have seen an SCR described as similar to a PNP and NPN transistor linked together. But any attempt to replicate the idea seems to fail. In the circuit below, for example, the LED is ...
0
votes
1answer
150 views

PnP NpN transistor circuit, Were would the mic jack go?

I know the circuit says to put the mic jack parallel to the speaker, but im not exactly sure were to put it. Also, could I use another speaker as the mic? This is the pnp npn circuit I found on the ...
1
vote
0answers
106 views

How to calculate voltages on guitar fuzz circuit with pnp and npn transistors?

I have built this circuit on a veroboard, and it seems to me that it has been wired correctly. I do however get a very low output from the circuit, approx 1/2 to 1/3 of the input signal. I reckon that ...
0
votes
3answers
105 views

what exactly is biasing in transistors and how to do biasing

I have read that collector, emitter must be reverse biased in CE configuration in npn transistor but how can n and n be reverse biased
0
votes
0answers
171 views

PNP and NPN transistor used with ARDUINO how to connect them?

This my circuit. What it does is: measuring pressure with MPX200A sensor and looks if pressure under 3 bar, switches on part 1 on arduino (2 transistors) to run DC motor clockwise. If pressure above ...
3
votes
1answer
577 views

Turn 9V device off using 3.3V logic level signal

i'm facing the problem to turn a 9V (battery) powered device OFF using the output of a 3.3V based microcontroller. To do this i already threw together the following circuit (which works - assuming i ...
0
votes
0answers
45 views

PNP collector voltage drop under fan load?

Im trying to build a circuit to drive a fan. Im following an example that i found online. R5 is a 10k thermistor R6 represents the fan to drive (starting resistance 70k). Its a 12v pc fan but it will ...
1
vote
0answers
85 views

NPN Transistor Noninverting Amplifier

I know how to design an inverting amlifier with a NPN transistor. Now I need to make a electret microphone amplifier to connect with Arduino, which only reads positive voltage values. Is there a ...
1
vote
1answer
192 views

If the depletion layer of a transistor collector/base junction is thick, why are majority carriers still collected?

In "Principles of transistor circuits, 8th edition" (top of p26) it is said that once holes have been injected in the base region by a forward biased base-emitter junction (which I understand) of a ...
1
vote
4answers
115 views

Transistor biasing problem

Suppose this is the biasing process of an NPN transistor. simulate this circuit – Schematic created using CircuitLab The battery to the left forward biases the emitter diode because its ...
1
vote
2answers
123 views

How to choose a transistor for amplification

I've been trying to find information on choosing an NPN transistor but everything I've found seems to apply to saturated transistors only. I'm basically trying to amplify the current given from a 3mm ...