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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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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35 views

CMOS: dual of cascode circuit

If this is a differential 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
52 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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49 views

DELL u2412m. Help identificate SMD [on hold]

Help identificate SMD. what is that? DVI port doesn't work Full picture
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0answers
32 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
99 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
53 views

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 ...
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2answers
70 views

what does it mean for a to BJT operating at the edge between the active and saturation modes?

ive recently been fascinated with diodes and was wondering how i'd design a circuit that works at the edge of the breakpoint between the active and saturation mode. How would the circuit be analysed?
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1answer
45 views

Max frequency of a component? [on hold]

For example, an SCR, is this the maximum frequency you can send a 'on' or 'off' signal from an Arduino to it, or is it the maximum frequency of say, 30V flowing through it? Please let me know, I ...
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2answers
32 views

BJT Amplifier in AC mode

In the lesson on BJT Amplifiers, we were told the we can find the AC equivalent circuit by replacing all capacitors by short circuits, inductors (if any) by open circuits, dc voltage sources by ground ...
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4answers
111 views

Use transistors to amplify a very small voltage

I'm new to electronics and I have a problem. I want to use a LED to detect light but the voltage it provides is very small (30 mV) and I don't think it can open a transistor. How can I amplify this ...
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2answers
49 views

Differences between current sources transistor and current mirror

In this configuration simulate this circuit – Schematic created using CircuitLab if the two pMOS are equal, they provide the same drain current to both the branches: suppose that Vbias ...
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0answers
59 views

AC electronic load (current sink) (Automatic test equipment for DC/AC)

I am contracting a automatic test equipment for DC/AC converter (24V-5A to 50V/2A). The core of the tester is the electronic load. The electronic load is a constant current sink as the circuit here. ...
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78 views

Transistor amplifier circuits

What is the ac collector resistance for the transistor Q1? I am having trouble finding which resistors are in parallel with each other in the circuit above. I want to find the voltage gain and power ...
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3answers
75 views

analysis of BJT PNP type

here is the question. As the hints states, we assume it is in Active Mode which means V(EB)=0.7 also, it is given that B=100, therefore, since Ic=B*Ib , gives us Ic=100*Ib now, I thought it is a ...
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2answers
85 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 ...
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1answer
44 views

How to remove degradation in voltage gain when replacing the original \$R_L\$ with a small value resistor?

For the following common-emitter amplifier, the original \$R_L = 4.7\space kΩ\$. When I replace it with a small value resistor (\$100\spaceΩ\$), the voltage gain will drop. Is there any way to drive ...
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0answers
21 views

Is there a rule of thumb or calculation to determine switching frequency with a baker clamp and/or speedup capacitor?

A baker clamp with a speed up capacitor can increase the switching frequency of a transistor. Is there a way to determine by what factor, or what the new limits are with these additions or is this a ...
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32 views

multiple RGB LEDS on minimal pwm pins VS current limitions

the theory explained at Hooking up multiple RGB LEDs while using a minimal number of PWM pins on an Arduino? isn't really working with the arduino current limitations mentioned at ...
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1answer
52 views

How do I troubleshoot this high-frequency PWM fan control circuit?

I have a 230 Volts fan from EBM papst. It is a fan that can be controlled through a PWM signal (between 1 and 10 kHz). I have built the circuit that is in the manual (see image) I did get this ...
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1answer
59 views

Power feeder scheme adaptation

I'm trying to change the voltage regulation circuit in order to obtain a different range of voltage. My feeder uses a diode bridge and a transformer, that are not displayed in the scheme(it works). ...
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1answer
41 views

How can I debug the amplifier section of tuxgraphic's powersupply?

I've built this circuit: http://www.tuxgraphics.org/common/images2/article379/powersupply.gif Here is a closeup of the amplifier section which I've built: simulate this circuit – ...
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51 views

Transistor to switch 10A 250V [closed]

Is there a transistor to switch 250V power supply to control lights & fans? I know there are relays to do this work but I need a transistor solution..
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1answer
45 views

Calculating high side switching resistor values, Vout, and heat

I added 3 high side switches, like below schematics. And all needs to turn 5V on and off. I have few questions about it. How do I calculate the resistor values ? I have few ideas but I want to know ...
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2answers
54 views

BJT In Reverse Avalanche Mode

I want to connect a BJT as a zener diode, that is operating in the avalanche mode when the Base and Emitter is reverse biased. My question is if the data sheet states the forward current for Base and ...
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1answer
86 views

Confusion about NPN transistor

I need to do some switching and I want to turn off both +ve and -ve(GND) I can use 1 NPN and 1 PNP transistor. But I'm wondering if I can use 2 NPN transistors only, I have some confusion about NPN. ...
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3answers
55 views

Parallel LED strings of different colors and Arduino

I need to use 7 strings of led, each one of a different color. I will control each string using a Arduino and the BC 337 Transistor. The string will be connected to a 12V power supply. I have read ...
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48 views

how to redesign the circuit to drive a 230V 100W lamp for 5 minutes

I have a circuit , the circuit operates with a siren using a 9v battery the siren used is UM3561 i want to replace the alarm part of the circuit using a RELAy that can drive a 100W 230V lamp for 5 ...
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1answer
58 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 ...
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3answers
74 views

BJT in Saturation

Is it possible for the base current to exceed the collector current for a BJT in saturation mode? (If the base current was increased without the collector current increasing at all)
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1answer
81 views

why do 2N2222 and PN2222 avalanche differently

i've been experimenting with a 2N2222 transistor (in the TO-18 metal case) and using it as an avalanche transistor -- by not connecting the base and having the emitter and collector connected in ...
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0answers
60 views

Coilgun troubles

I am trying to make a coil gun and I'm following a design made by Mehdi Sadaghdar the link is below. http://www.electroboom.com/?p=101 I am having trouble with my IRF540N nmos transistor. At first I ...
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149 views

Use one or two transistors to switch an LED from PIC

I'm fairly new to electronics - I've had a reasonable amount of success with getting PCBs made using Eagle, but it was mostly wiring together breakouts and fairly simple stuff. I've spend the last two ...
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3answers
111 views

Using a 1.5V battery to increase the voltage from a headphone jack so it can switch a transistor at lower volumes

I recently built a circuit using a 2N3904 BJT transistor with the hopes that when connected to a headphone jack, it would light a LED whenever an audio signal was passed through. However, I found ...
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1answer
44 views

Ballpark achievable switching frequency for 100mW D-class amplifier

The background for this question is a Master level university group project, we're designing a class D sigma delta modulated amplifier which is part of a MIDI synthesizer on a large FPGA. We're ...
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1answer
41 views

NMOS Channel Type

I've seen some conflicting information about the inversion channel for an NMOS device. Is NMOS n-channel or p-channel? And is the substrate n or p? I know PMOS is just the opposite for both and the ...
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Basic transistor questions

I've created the circuit shown. I'm using a 9V battery (actually throwing out 9.53V) and 5V coming from an Arduino to test with both 9 and 5 volts. The transistor is a BC 548B (datasheet I'm using is ...
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3answers
126 views

Relay not switching correctly, controlled from ATtiny85, output to motor

I have an ATtiny85 switching an NPN transistor, which will in turn switch on a relay that will run a motor. Everything is run off a 3.7V 18650 Li-Ion battery, but I have since moved over to a variable ...
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1answer
36 views

JFET voltage divider bias calculations

Hi im having some trouble with knowing how to perform calculations for \$I_D\$ in a simple JFET where it is biased by means of a voltage divider. I understand that use of the equation: $$I_D = ...
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3answers
75 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 ...
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2answers
64 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 ...
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2answers
71 views

Correct circuit element alternative to transistors

First please see my proteus file to understand what am I trying to do. http://www.docdroid.net/ru27/yenitasarim.pdf.html As you see, there is 5 button groups vertical and 5 button groups horizontal. ...
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7answers
290 views

Understand transistors

I can understand some of the electronics concepts and components, like diodes, resistors, thyristors, capacitors, inductors. But transistors I still fail to grasp the way they work and what role they ...
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67 views

Transistor Common Base configuration

It is said that for a common base configuration the base is grounded, i.e at zero potential. But at forward biased for a npn transistor, the battery used to forward bias emitter base junction is ...
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1answer
166 views

Does reverse biasing hold any meaning in case if both terminals are n type semiconductors?

When we talk about an n-p-n transistor in common emitter configuration, we often say that emitter-collector circuit (the one towards right) is reverse biased. In what sense it is reverse biased? Here, ...
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49 views

Blade Nano QX Charger hacking

I've got a Blade Nano QX micro drone. It's awesome. It arrives with a USB charger for the 150mAh 1S lipo battery, that has one very annoying feature. When it's charging a red LED is on, and when it's ...
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2answers
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Resistance as a function of base voltage in a transistor

In this very interesting introductive video https://www.youtube.com/watch?v=CkX8SkTgB0g, I learned that a transistor is basically nothing more than a resistor whose value changes accordingly to what's ...
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Ripple in simple common emitter DC amplifier output

simulate this circuit – Schematic created using CircuitLab Hi. I am experimenting with this circuit to drive a piezo stack actuator. The piezo actuator will be connected across the ...
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66 views

NPN vs PNP Transistor Wiring

Whilst reading about differences between PNP and NPN transistors I came across the following circuit diagrams: ...
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85 views

boiler switch transistor

I'd like to switch a boiler on and off electronically. It is now connected to a thermostat. The first thing I did was measuring the current flowing, closing the circuit with a multimeter set to DC. It ...