The transistor is a semiconductor device that can amplify signals and switch power. Most used types are bipolar (BJT, for Bipolar Junction Transistor) and MOSFET (FET, for Field Effect Transistor)

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The Transistor Menace - Questions regarding an Arduino rgb LED project

I've been browsing this forum and the internet now for a couple of days and what I thought would be an easy side project turned into a (for me) quite complicated matter. I'm planning to build a mood ...
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28 views

External power source steered by arduino through transitors - voltage differences?

I'm trying to steer rows of leds through arduino and I came into some difficulties. My circuit is inspired by instructable: So I have something similar to this grid of resistors and transistors on ...
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2answers
76 views

Current limiter its not working as it should?

I have created a voltage regulation circuit using op amp and feedback resistors, now I am trying to add a current limiter to the circuit. have read how to create this using two transistors and a ...
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3answers
63 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 ...
2
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3answers
140 views

Basic common emitter circuit: voltage reduction at the output

I have a basic circuit for converting the 3.3V signal of a microcontroller board to a 24V constant voltage needed to control a device switched by voltage. When I measure voltage at the output while ...
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1answer
44 views

Power circuit design logic — suggestion

I am designing a board where my Microcontroller is powered by LM7805 regulator & my load requires 3.8 voltage, is powered by following voltage regulator NCP57302. ...
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3answers
98 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. ...
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2answers
83 views

Transistor or relay instead of button

I'm trying to make a circuit that will press the reset button on the device after a power failure. This should reset the device when the power is restored and remains inactive until the next power ...
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1answer
30 views

Selectively outputting 2 inputs based on a third input

I currently have 2 inputs that can be on or off, they could be 00, 01, 10, or 11. I want to output them only if a third input is active. I figured BJT transistors would do the job, but they seem ...
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1answer
79 views

Bipolar transistor amplification biased

I'm having some trouble trying to solve this exercise. It is a BJT transistor common emitter circuit, with a biased resistor between the base and the collector. I am supposed to compute the signal ...
3
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1answer
72 views

What does “Sourced from process <number>” mean in transistor datasheet?

On first page of Fairchild BC516 transistor datasheet it's written: Sourced from process 61 What does it mean? Is it important for part's users or it's some kind of production process ...
2
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1answer
94 views

problem with making 1 bit RAM memory using transistors?

I'm trying to make 1 bit RAM using four transistor ( 2 NOR Gates ). I built the 2 copies of the following circuit: I connected a LED to the output "F". Also, I connected Another LED to the output ...
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1answer
53 views

Two transistor temperature sensor

Background I was considering making a temperature sensor from some NPN transistors. I read the Wikipedia page on Silicon Bandgap Temperature Sensors (can't use more than 2 links...) and this piece ...
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1answer
50 views

Need help understanding LCD Power Enable circuit

Here you will see a schematic for an LCD panel. Header on the right, panel on the left, backlight power circuit on the bottom left and enable circuits in the middle. I am having difficult ...
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2answers
39 views

MOSFET N channel power switch: high side doesn't work and low side would need multiple MOSFETs

I'm experimenting with a MOSFET that controls power to another component so that I can remove all current from it when it's not in use and save power. In regards to that, this question is awesome: ...
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1answer
47 views

BJT driven LED lengthy fall time

I am designing a circuit for a strobe amplifier and am having some difficulty with the LED emitting light for longer than expected. I am measuring the light out of the LED with a photo receptor ...
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3answers
145 views

Component to short 2 wires when powered

I am attempting to short 2 different wires, call them A and B when C I'd powered. I am attempting to use a transistor, but when I attatch C to the base and A or B to the emittor, it just powers A/B ...
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2answers
40 views

PNP transistors and processor pins

On the diagram below, there are 4 PNP transistors. When RA0 is set to HIGH, then current flows from +5V through RA0 to GND and from +5V through 7 segment display, then through (for example) RB0 (if ...
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2answers
72 views

Optoisolator not turning off

I'm using an optoisolator for high side switching a Nixie tube. For some reason, the optoisolator is not fully turning off, allowing the a very minimal amount of current to flow through the Nixie ...
2
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2answers
71 views

How do I use a PWM unit and/or microcontroller to have transistors progressively all turn on and then progressively all switch off?

How do I use a PWM unit and/or microcontroller to have transistors progressively all turn on and then progressively all switch off? It's for what will most likely be an 18-pulse inverter. ...
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1answer
36 views

Load resistor value for phototransistor switch

According to this application note from Fairchild (btw, I find Fairchild's application notes to be of immense value - thanks to all who have taken the time to write one), the load resistor value for a ...
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1answer
36 views

Programmable Unijunction Transistor Circuit

I am currently teaching my self electronics and have a question about PUTs. I am wondering why there has to a resistor on both sides of the PUT in this circuit: Please note that I have already read ...
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1answer
84 views

Why doesn't my MOSFET switch off?

In the following circuit, LEDPWR goes the power lines of some digitally addressable LEDs. But the LEDs are not always on, and even when they are not being lit, they ...
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2answers
170 views

Can you use a single Bipolar Transistor as an AND gate?

I have recently began electronics as a hobby, and I am curious about the use of Bipolar Transistors in AND gates. Simply put, if I was to use the collector and base as inputs, and run small (~1 volt) ...
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1answer
81 views

Transistor shortcut

i would like to fade an led strip using pwm with a n mosfet led that is commanded by a two way switch ( relay and sw1 ) like this: simulate this circuit – Schematic created using ...
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2answers
92 views

In the real world, what happens if a transistor turning on causes it to turn off?

So say you have the following circuit: I apologize if this circuit is super simple, but I have very little electronics knowledge. The program I'm using will be for building circuits out of ...
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1answer
103 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 ...
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0answers
56 views

LTSpice showing negative transistor power

I'm using LTSpice to model a LC oscillator, driven by a NPN transistor. When I used the power calculating function on the transistor, LTSpice indicated that during part of the cycle the power ...
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3answers
77 views

What kind of component would I need to put a break in a RS-485 bus?

I'd like to have some kind of electronically controlled switch (transistor, relay, solid-state relay, etc) that acts as a break in a RS-485 bus. The effect I would like is to optionally split the bus ...
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1answer
109 views

Transistor Choice for LED Control Circuit

I just completed an introductory course in digital design. During the course I designed a circuit for driving multi-color LED's with an automotive application (for a personal project). The following ...
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2answers
82 views

Replacing a switch with MOSFETs

I currently have a 2:1 switch / multiplexer which is being used to switch between two different batteries which are to provide power to a small module on my board. The switch that I am using is the ...
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2answers
46 views

TIP 120 vs TIP141

I was wondering what are the major differences between TIP120 and TIP141? Currently it seems they are both NPN, but TIP141 can handle a larger current. Would these two be interchangeable? I am ...
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3answers
81 views

Slightly weird astable oscillator in a 555, where does this capacitor discharge to?

In the 555 datasheet, the cap is usually connected to pin 7 (discharge), but in this circuit, it's not: When the capacitor voltage is >2/3Vcc, output will turn off and current will have no where to ...
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2answers
53 views

unexplained short circuit with PWM signal?

Something happened that i haven’t been able to explain , I wrote a program to output a PWM signal, this to activate a transistors base using a PWM which I could change the frequency using a ...
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1answer
77 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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2answers
99 views

Switching Piezo Buzzer with a Transistor

I want to be able to switch a piezo buzzer with arduino without connecting it directly. I have wired the following circuit I found on the internet: The problem is that the voltage across the ...
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3answers
69 views

Can I use 1 resistor for both inputs of an RTL NOR gate?

I am working out the ideal RTL NOR circuit to use as universal gates for a large project. Based on what I've found on Wikipedia, to implement a NOR gate using BJTs and resistors, we have the ...
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2answers
77 views

differential amplifier will cancel DC present at input

In differential amplifier, it is written that "only AC signal will be amplified and DC part at the input will be canceled and hence there is no need of DC blocking capacitor". I am not getting this ...
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108 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
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1answer
165 views

A circuit having 2 inputs and 2 outputs

I am going to design a circuit that should have 2 inputs and 2 outputs. when both inputs are low both outputs should be low when input 1 is high and input 2 is low, output 1 should be a square wave ...
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2answers
78 views

2N6027 variants

I am trying to build a simple LED flasher circuit with a PUT 2N6027. I have a bunch of transistors and some are marked 2N6027 110, and some are marked 2N6027 B09. When I use the B09s, I have no ...
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2answers
87 views

How to drive 50 LED from a 3.3V MCU

I have an Arduino DUE, that is based on an Atmel SAM3X8E ARM Cortex-M3 CPU. It has 54 Digital I/O. It works on 3.3V. I'd like to use it to drive individually 50 LEDs (for instance 50 optocoupler to ...
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0answers
40 views

how to wire up 2 separate ultrasonic transducers

Okay I have 2 separate receiver and transmitter and i've seen this post and it does tell me how to hook up. But why do I need all the transistors and resistors? Why cant I just use the 5v pin, ground ...
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3answers
111 views

Discharging capacitors upon power loss

I have designed a power delay switch which is intended to cause a short delay while a reservoir capacitor fills up before giving power to my microcontroller due it needing a short burst of high ...
0
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1answer
70 views

Arduino Motor Control Circuit with Power Transistor and H-Bridge

I'm new to motor control, and I'm trying to create a circuit to control this motor: http://www.robotshop.com/en/banebots-rs-550-motor-12v-19300rpm.html The key electrical characteristics for my ...
2
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2answers
86 views

Momentary switch power: press to turn on, microcontroller can turn itself off

So I have this circuit here. Ideally, it allows a momentary switch to connect the power circuit, and when released it would stay on. Here's what I think this circuit does. The button is pressed ...
3
votes
4answers
114 views

Parallel Transistors in Constant Current Load

I'm designing a constant-current dummy load for testing my power supplies. This load should be able to handle a maximum of \$2\mathrm{A}\$ at \$24\mathrm{V}\$. My current design, so far, is loosely ...
0
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2answers
118 views

Identify unknown transistor (possibly faulty LM35 temperature sensor)

I have a transistor I know practically nothing about. It was included with an Arduino I got off the internet. It has the words 36RA, LM35, and DZ on the flat side of the plastic. I have a digital ...
0
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2answers
74 views

transistor voltage drop

I'm having an issue with a transistor. I'm apply ~3.3v to the base, 4.7v to the collector, but only getting ~2.5v from the emitter. I need to be getting close to the full 4.7v I'm aware there is ...
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1answer
52 views

Transistor Emitting Without Collector [closed]

I'm pretty new to the hardware side of electronics and am building some basic logic gates. The first Im trying is an AND gate and the problem I'm having is that whenever I power the base of the ...