Questions tagged [transistors]

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

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6
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2answers
631 views

Transistor in saturation mode?

I was wondering why do we so often want out transistor to work in saturation mode? Ie. For a MOS Current Steering Circuit we want our transistors to operate in the saturation region....
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1answer
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MOSFET Turns on without voltage on the gate?

I am using the following transistor to turn a motor on and off: http://pdf1.alldatasheet.com/datasheet-pdf/view/418991/INFINEON/IPP096N03LG.html I am applying 12V to the drain and 0V to the gate... ...
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Question about the basic differences between a MOSFET and a FET

I'm still new to all this stuff, but I'm slowly trying to understand. I'm getting most of my information from "Getting Started in Electronics" (Forrest Mimm's book) Okay, so MOSFETs allow current to ...
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1answer
188 views

Transistor terminal impedence?

Can some one explain the concept of transistor terminal impedance? What is it, and why is it important? Any links to useful notes/resources will also be greatly appreciated.
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4answers
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Intrinsic Gain vs. Voltage Gain

I was wondering what the difference is between intrinsic gain and just "normal" voltage gain of a circuit i.e Vout/Vin?
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Low power, low voltage, slow (0.1Hz) oscillator?

I had the opportunity to analyze a very interesting circuit today using a programmable unijunction transistor as a timer. The power supply varies, and the circuit must operate on under 10uA of ...
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3answers
367 views

From Transistor to Gates

Does anyone know any links, books, tutorials etc. that will help me better understand how transistors are used to design gates/functions? Here is a link that does a good job of explaining the basics. ...
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Replacement for 2N6027

I am working my way through Make: Electronics. For some experiments in this book, you need a 2N6027 programmable unijunction transistor (PUT). The shop I am buying my parts from doesn't have this ...
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2answers
8k views

When to use what transistor

So there are several types of transistors: BJT JFET MOSFET Combine all that with the various flavors of each (NPN, PNP, enhancement mode, depletion mode, HEXFET, etc) and you've got a wide array of ...
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Switching DC with MOSFET: p-Channel or n-Channel; Low Side Load or High Side Load?

I think, it is time I understand working principle of MOSFET transistors... Suppose that; I want to switch voltage on a resistive load by a MOSFET transistor. Any control signal between -500V and +...
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3answers
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Equivalent circuit of a solid state relay

I want to switch 50V AC voltage. Maximum drained current will be 5A. Frequency is 50Hz. Switching speed is not important, can be real slow, it is not a problem in my application. I wanted to use ...
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2answers
41k views

How can I find a replacement for a transistor?

I have a circuit that uses BC106 and 2N3634, which can't find in store (where I live). Is there any website which could help me find an equivalent transistor? For instance I want to replace BC106 and ...
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How does this transistor work?

The picture shows a detail of schematic diagram of the LM555. I presume the horizontal line is the base, but I'm not sure I understand how the transistor works. What is the effect of connecting base ...
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Strange (flyback?) diode in a circuit with a transistor switching an inductor

Edit: The following question is related to a perpetual motion machine, a "Selfrunning Free Energy Muller MotorGenerator powering a 20 Watt bulb" The switching device shown on the circuit was ...
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How is this use of a transistor?

Im working with a LM3915 makeing a vu-meter. I dont think the LM3915 will directly drive more that 1 LED. I'm looking to find a way that I can hook up more that 1 led to the LM3915. I think that ...
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1answer
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What transistor do I need to drive many LEDs and how should I hook it up?

I know that a transistor amplifies a signal, but I've never used one. I have this design here and I want to add 15 LEDs connected to each pin, instead of 1. How I could incorporate a transistor to ...
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1answer
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AC and DC supply from Arduino?

Does the Arduino Uno supply AC or DC power when connected to the computer via USB? Can we specify is we want AC or DC? I am trying to build a circuit that has a transistor but I don't currently ...
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Best way to get +5V or +12V or 0V from arduino pin

I am working on an eeprom programmer as an Arduino shield. There are two pins on my EEPROM that require a 12V signal as part of the programming process. One of them is an address pin that I am also ...
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4answers
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Is this a proper use of a PNP transistor?

I'm attempting to use a transistor to switch on and off an SSR, which in turns switches on and off a solenoid. I originally used an NPN transistor (2N222), but this caused problems when the MCU ...
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transistor as low-leakage diode

I found this application in AD's OP77 datasheet: Apparently they (ab)use a 2N930 transistor's B-C's junction as a low-leakage diode. Is there any reason why you would choose a transistor over a ...
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324 views

Finding a Transistor and Other Parts

I consider myself only a novice when it comes to electronics... I can dissect most consumer electronics and figure out how they work; however I am having issues getting over the learning curve when it ...
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2answers
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Totem Pole Output Driver

I was wondering if someone could explain what a totem-pole output driver is? I have seen the term mentioned in connection to the inner circuitry of an AND gate (consisting of transistors) and in ...
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Need an XOR gate that works up to 2 to 3 GHz

I have encountered an unusual situation in which I require an XOR gate that will function reliably when presented with a square wave input with a frequency between 2 and 3 GHz. I know that desktop ...
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What kind of resistors do I need to use in this Canon remote switch, if it is possible at all with the P2N2222A transistor I have?

I'm a total electronics n00b set out to create an intervalometer for my Canon EOS 350D camera which seemed super simple from the outset, but I got a bit blocked with creating a switch using a ...
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5answers
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Why is a MOSFET triggered by Vgs and not Vgd?

Looking carefully at this diagram of one type of MOSFET: (found in this application note) We can see the device is virtually symmetrical. What makes the gate reference itself to the source and not ...
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How do transistors replace the electromechanical switch in an inverter circuit?

Quoting from wikipedia: "In one simple inverter circuit, DC power is connected to a transformer through the centre tap of the primary winding. A switch is rapidly switched back and forth to allow ...
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Unnecessary pull down resistors on BJT and FET transistors?

I commonly see weak pull down resistors at the base of NPN transistors. Many electronic sites even recommend doing such things, usually specifying the value as something like 10x the base current ...
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Basics of Transistors

something has been bothering me for awhile. When I look at a circuit involving anything more complicated than RLC components (and perhaps op-amps) I struggle to figure out what it's doing unless its a ...
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1answer
162 views

Transistor bins - effect on speed

Let's say we have vanilla BC846 (80V), BC847 (50V), BC848 (30V) transistors from the same company, each with 3 bins A, B, C where C supposed to have to highest hfe. Is that correct, that BC846C ...
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3answers
2k views

Faster alternatives to BC847C / BC859C

I wonder, are there faster jelly-bean alternatives to BC847/859 (i.e. low-voltage, low-power, SOT23, high-speed transistors)? BC847/859 are rated for 100Mhz, something at 250-500 (and even 1000) ...
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1answer
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Expected values for \$V_{BE}\$ in darlingtons

In this answer @stevenvh points out that \$V_{BE}\$ for a TIP110 darlington may be as high as 2.8V. This looks extremely high to me, even for a double junction. In normal use you don't need to drive a ...
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Driving piezo buzzer from MCU pin

I'm looking for the right circuit to connect my piezo buzzer to MCU (STM8S in my case). I don't have a partnumber\datasheet for my particular buzzer, but I've found a number of similar schematics in ...
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2answers
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limiting base current to BJT

I'm actually working with a darlington pair of BJTs. My question is if I need to put a 1kohm resistor between my MCU pin and the BASE to use it as a switch. Since the Hfe ratio for my transistor is ...
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Do I need to duplicate the 4th “substrate” connection when building CMOS gates out of discrete transistors?

All CMOS digital integrated circuits I've ever seen connect all the nFET substrates together to GND. In particular, the IC CMOS NAND gate has one nFET that has its substrate connected to GND, but its ...
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1answer
749 views

Voltage controlled voltage source

I am designing a high powered LED driver controlled by a microcontroller. Now it would be very easy to make a constant current limiter so I don't burn out my LED. I have a bunch of LM317's and ...
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3answers
517 views

How are low-noise transistors different from other?

Yes, I know: they have lower noise levels. What I mean is how is this achieved? And I guess there must be a trade-off as well (otherwise all transistors would be made as low-noise?)
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580 views

Contemporary transistors

I found the following statement on Richard Dawkins book The Selfish Gene (1989): "... there are some ten thousand million neurones in the human brain: you could pack only a few hundred transistors ...
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1k views

How to choose a switch?

There seem to be about 4 major flavors of transistors, and then there are NPN/PNP versions. There are also relays, SCRs, and TRIACs. When I need an microcontroller-controlled switch, what rules of ...
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2answers
590 views

Transistor switch: How to commutate 4-6V rail with 0-3.3V signal?

I want my gate (fet) or base (BJT) to turn on at 3.3 v, I then want to have 4 - 6 volts on my collector or drain, and the same voltage as the C or D to be present on the emitter or source,how should ...
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2answers
144 views

100Ω and High-speed data lines

I just had a problem with some lines coming from a PIC IO bank, and going into the base of a transistor (BC635) at some high speed. Without any base protection (since the PIC can't provide enough ...
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10answers
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How can CPUs be stable when they have so many transistors?

As we know a CPU is pretty much billions of transistors on a single thumbnail, what if one of the transistors breaks? Does CPU have any auto-recovery mechanism?
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Vacuum tube systems in apollo era space missions

I hope this is the right place to ask this. But my friend is just learning about electronics and just was given an old vacuum tube. Just because I'm curious, is there any technical information on the ...
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4answers
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Explain small signal model of transistor to a beginner [closed]

I am a little weak in analog circuits even though electronics is my subject (Engineering course). Transistor is like a Pandora box to me. Last day I read a question about how to use transistor as ...
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5answers
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Explain what is a transistor in plain English!

Can someone care to explain - in plain English - what a transistor is and how it works. I know computers are full of these but don't know much about them. P.S. I know about this site from another one ...
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3answers
9k views

Potentiometer vs. Transistor

From what I know, potentiometers vary an analog current with an input usually in the form of a knob. And transistors vary an analog current with an input in the form of a smaller current. Is there ...
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2answers
10k views

NOT gate with PNP transistor

I'm trying to make a NOT gate, but with a PNP transistor instead of NPN. What would a wire diagram look like for a NOT gate with a PNP transistor?
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6k views

Is 2N9013 a good replacement for 2N3904?

I needed 2N3904 transistors, so I went to the few (poor) electronics shops we find in my country. They didn't have those, but they gave me 2N9013 and stated that those were equivalent NPN transistors. ...
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1answer
244 views

Diffusion capacitance approximation for bipolar power transistor

I'm trying to remember the approximation for the value of the diffusion capacitance for a bipolar power transistor. I think it might have been gm/Ft? Can anyone confirm this and/or give a reference? ...
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2k views

configuration of transistor for amplification

why common emitter configuration is used more than common base configuration of transistor for amplification purpose? when common base configuration provides more stability than of common emitter ...
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2answers
1k views

Operation Amplifier with Transistor output

Is there a name for feedback amplifier topologies which include an opamp and transistor in the feed-forward path?. I need to design an amplifier with high bandwidth (almost 100 MHz) and high gain (50) ...