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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2 LED Parallel circuit help?

I need to make a circuit with 2 leds, 1 green 1 red. If the current flows, green led will light up, if there is a break in the circuit (open circuit) it will light up another led as red. I don't ...
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73 views

How to have transistors working with copper computers all around? [duplicate]

I have 60 lbs. of copper, and before selling, I intend on using all of its 60 lbs. of free electron movement to power a homemade computer. I would like to have MOSFETs connected to the copper ...
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92 views

How to make a computer with only copper? [on hold]

I have 60 lbs. of copper, and before selling, I intend on using all of its 60 lbs. of free electron movement to power a homemade computer. I would like to have MOSFETs connected to the copper ...
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1answer
59 views

Class AB amplifier becomes hotter, using more current and then becoming even hotter

In the circuit above a Class AB amplifier (this is one also called Class A+AB) can be seen with Q1 and Q3 used to get the current biasing voltage for Q2 and Q4. transistors Q2 and Q4 become hotter ...
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70 views

How to level shift an analog signal?

I have a sinusoidal input signal (with a swing of 100mV roughly) centered around 100mV (DC). This signal needs to be input to a CMOS inverter. For this I need to level shift my signal around the ...
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1answer
79 views

Strange LED behaviour

simulate this circuit – Schematic created using CircuitLab I have +9v connected via 180 ohm resistor to the collector of an NPN transistor. The emitter is connected via 680 ohm resistor ...
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1answer
61 views

DC motor - Transistor / Mosfet - Design

The one on the left seems to work neatly. But the right ones' motor goes way slower. Though, I did find the right one on the internet (and internet is always true). My thoughts: The amount of ...
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35 views

Calculating operating point for circuits with more than one transistor

Whenever I see an amplifier with more than one stage I got no idea how to start calculating its operating point. In some examples which I have analysed in book it was written "we can see that base ...
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1answer
28 views

Circuit for amplification and protection against input inductive spikes

I'm working on a permeability measurement project and my setup includes a primary as well as a secondary side of a coil. I need to measure the flux through the coil, hence on my secondary side I have ...
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2answers
124 views

Selecting a transistor for high-side switching at 5V with a 2A load current

I'm doing a high side switching of 5V 2A load and will be ON or OFF for long time(1-10 hours). Now I'm confused about which transistors should I use ? or MOSFETs ? Do I need heatsink ? I really ...
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41 views

TIP31A equivalent [on hold]

I'm am about to print out a PCB in order to build a metal detector. Here is the design: Twin Loop Treasure Seeker I am missing a transistor, a TIP31A. I have looked in an alternative transistor ...
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1answer
52 views

How to find the Q point of the NMOS trsistor in Voltage-Divider Biasing Circuit?

The following is the circuit needed to be analyzed to find the Q point(\$V_{GS_Q}, V_{DS_Q}, I_{D_Q}\$). \$V_{TN}=1\text{V}\$ \$K_n=0.5\text{mAV}^{-2}\$ simulate this circuit – Schematic ...
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30 views

High voltage, low current switching

I am using a high voltage low power integrated circuit (tracopower). I need to siwtch the output with a square wave signal up to 500 Hz. The problem is high voltage transistors also work with high ...
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47 views

Use an 800 ma stepper motor with a 500 ma uln2803

Is it possible for me to use this stepper with this IC? I am using the second schematic on this page. I do not want to use the transistors in series if I don't have to. Thanks.
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34 views

MOSFET T-model question

In the attached diagram, I do not understand why the current source I becomes an open circuit and the voltage source Vdd becomes grounded. If someone can clear up this simple question for me, it'd ...
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2answers
62 views

Can I connect Arduino ground to the negative terminal of a battery?

I wanted to use a transistor to switch a circuit that has its own power source (a battery). It appears you could do something similar if you had two battery power sources, but in simulators, it ...
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1answer
32 views

Alpha/Beta Parameters of BJT

The BJT Current equations are given as :- IE = IC + IB IC = \$\alpha\$ IE IC = \$\beta\$ IB Does the relations with \$\alpha\$ and \$\beta\$ parameters include the reverse saturation current ...
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66 views

Connect lm386 to flash LED, dim light, poor sound

I'm really new. Not great in drawing schematics. I have a lm386 I want to connect to a tip31. I followed wherever I could online. 1. I tried it before the amp, so the sound became really loud and ...
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28 views

Equivalent circuit model of phototransistor

I would like to know the equivalent circuit model for a phototransistor. Is there an Ebers-moll model representation? Thanks
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20 views

Common drain CMOS single stage amplifier with current bias with positive and negative rail analysis

I was presented with a classical problem where i am asked to evaluate the output of this circuit when VIN = 0 and then 5 volts. The NMOS will be off as long as Vgs is less than Vtn. The NMOS will ...
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3answers
171 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 ...
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1answer
59 views

Replacing a relay by a transistor

i'm new in electronic, I made a simple circuit to control a pump it's working, but i'm really not happy of the result. I have to plug 2 power sources because if I have only one for the pump and the ...
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21 views

Two position soft-latching switch

I am building a secondary board to assist a primary board in the switching between two separate logic devices. The primary board uses a momentary push button to switch between the two logic devices, ...
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52 views

Mosfet small signal input resistance from source

Considering the T model of MOSFET for small signals I want to obtain the input resistance from source to gate. simulate this circuit – Schematic created using CircuitLab The current ...
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2answers
59 views

N-Channel MOSFET as 12 VDC switch

A little background: I have a 12 VDC "cigarette" socket in my car which is a non-switched circuit (so, always on). I'm in need of a switched socket, whereby power is cut when the car is not running. ...
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43 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 ...
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136 views

Weird voltage measurements on transistor

Just as an experiment, I decided to put together the following "circuit": I then went ahead and measured Vbe, Vbc and Vec and this yielded the following results: Vbe = 0.602 V Vbc = 0.589 V Vec ...
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89 views

Help me fix my logic circuit

I'm trying to learn more about electronics. So to do that I decided to implement boolean logic gates in a circuit simulator. So far I have made NOT, AND, NOR and a S-R latch. I wanted to try connect ...
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252 views

A question about Transistor in forward-active biasing?

I have question about transistor biasing. Between picture 1 and 2, what's difference, why we add the resistor RE in pic 2 ? what's it effect to circuit ? Similarity for pics 3 and 4, instead of ...
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52 views

can NPN transistor be used when sinking current?

so to give a little bit of background, I want to experiment with led matrixes. I have multiple Arduino Nano boards, and have done small projects (9 LED bank with simple animations). So I know that ...
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2answers
85 views

How can I make the dimensioning of a temperature monitoring circuit?

I need to design a circuit to measure temperatures in the range 15-40 degrees C (this will later be the basis for a regulator of a peltier-element for a fridge). I tried a circuit using the ...
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2answers
79 views

When and how is a protective diode applied to the collector of a transistor switch?

I'm confused about a passage in "The Art Of Electronics", by Horowitz & Hill, regarding protective diodes in transistor switches: ...
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3answers
74 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 ...
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110 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 ...
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677 views

Why drive a relay with a transistor switch?

It appears most people drive relays through a transistor rather than directly from a digital output pin on an Arduino. I had wired the output pin directly to my relay before realizing this and it ...
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68 views

How does base resistance affect a transistor?

I'm not strong with electrical engineering and I have prototyped a circuit which works; however, to my chagrin, I don't understand why. I'm using an Arduino digital out pin to power a relay. I have ...
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2answers
126 views

Generating 12V PWM from 5V PWM

I am generating a 5V PWM signal from my MCU (an Atmel ATMEGA1284P). I need to convert this to a 12V PWM signal. For this I designed the circuit below, something very similar to a Sziklai pair, but ...
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115 views

How does the circuitry work in the Symet robot?

I ordered this Symet robot kit and it only includes instructions on how to build the thing instead of actually teaching you exactly why and how it works. I even ordered this book that walks you ...
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3answers
82 views

What is the correct transistor for this switch?

Ive provided a crude paint drawing to explain what I need done, basically I need some way to propel a high voltage motor with a low voltage microcontroller, using "pin 2" to trigger a current to run ...
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1answer
79 views

light up a 5v led with arduino

I need to build a big 6 digit display using 7 segment displays controlled with an Arduino, but the every display I find uses 5V LEDs like this one: ...
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25 views

Turn on/off serial and I2C display [duplicate]

I have 2 character display, one is controlled by serial another is controlled by I2C. I could control both with serial or I2C alone. But that's not the point. Now what I want is, to completely turn ...
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2answers
69 views

Effective transconductance of a CMOS inverter

If we have a CMOS inverter operating in its' linear region, what would be the effective trans conductance of the inverter?
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1answer
87 views

Transistor on by default

rookie guy here. I am experimenting with a control circuit for making an LED cube, but discovered some wierd abnormality in the transistors i was using. I wanted to test the circuit by replacing an ...
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1answer
37 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 ...
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1answer
85 views

Input Impedance of amplifier circuit

Why we need to consider the emitter resistance re while calculating input impedance of the given amplifier circuit? Is this a compulsion? I found out that even in case of common collector amplifier ...
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2answers
90 views

CMOS: dual of cascode circuit

If this is a differential folded cascode CMOS amplifier simulate this circuit – Schematic created using CircuitLab (where the "first" stage is nMOS and the "second" one is pMOS), can the ...
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1answer
66 views

Close circuit after a couple of seconds

First post on this site, sorry if it's too basic. I'm learning to interface with a particular chip which has a GPIO pin. I'm using the GPIO for input with a pullup resistor and a switch between the ...
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38 views

Erogation of current in Mosfet during saturation [duplicate]

When a nMOS transistor operates in the saturation region, its channel is pinched-off, as shown in this image and this image. So, the channel does no more connect the source with the drain, but a ...
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2answers
153 views

Controlling 10 high power LED with a Raspberry Pi

I'm trying to figure out how to control 10 Luxeon Rebel LED (700mA) from a Raspberry Pi. I want to be able to turn them on and off from code, but I don't need to have two or more LEDs turned on at ...
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2answers
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Beefcake relay control kit - Sparkfun

http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Components/General/RelayBoard-Large-v16.pdf I'm trying to determine the base current of the NPN transistor but keep getting numbers an order of ...