Questions tagged [transistors]
A transistor is a semiconductor device that can amplify signals and switch power. The types that are used most are BJT (Bipolar Junction Transistor), UJT (Unijunction Transistor), and MOSFET (FET, for Field Effect Transistor).
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Relay vs. Transistor?
Rather basic, I'm afraid, but when would you use a relay, and when would you use a transistor? In a relay the contacts wear out, so why are relays used at all?
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When is a MOSFET more appropriate as a switch than a BJT?
In my experimentation, I've used only BJTs as switches (for turning on and off things like LEDs and such) for my MCU outputs. I've been repeatedly told, however, that N-channel enhancement-mode ...
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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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Why are there so many relays used in a car, instead of transistors?
Recently I did some work on my car electric circuits. I see many relays are used in car circuits. These relays are used for simple switching, and I wonder why these circuits are based on relays and ...
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How do I saturate an NPN transistor?
I understand that in "saturation mode", a BJT functions as a simple switch. I've used this before driving LEDs, but I'm not sure I understand clearly how I got the transistor into that state.
Does a ...
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Why would one drive LEDs with a common emitter?
I've seen tutorials aimed at beginners suggest the way to drive an LED from something without enough current drive is this:
(option A)
but why not this:
(option B)
Option B seems to have some ...
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Why don't we make CPUs with 1000s of layers to make use of space in the third dimension?
I am wondering why don't we make processors such as CPUs with 1000s of stacked layers to make use of space in the third dimension now that we have three-dimensional transistors. To be clear I'm ...
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I don't care how a transistor works, how do I get one to work?
Every reference I can find on transistors immediately launches into theory-heavy alphabet soup. The above seems also to be assumed knowledge for reading a datasheet. I don't care; I just want to get ...
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Why do you need 2 resistors when hooking up a transistor as a switch
What is the point of R2 in the following diagram:
I get that R1 controls the current to the Base, but what does R2 do?
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Why are NAND gates used to make AND gates in computers?
Why is this a standard for AND gates
when it could be made with two FETs and a resistor instead?
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Why would an op-amp use BJTs over MOSFETs?
I've always been told that ideally, op-amps have infinite input impedance. So when I was looking at the LM741's transistor level schematic, I was confused when they used BJTs instead of MOSFETs.
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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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Which configuration is better for pulling down an NPN transistor's base?
I was discussing on pull down resistors with a colleague of mine. Here are the two configurations for transistor as a switch.
The input signal can either come from a microcontroller or an another ...
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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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Why do CPUs need so much current?
I know that a simple CPU (like Intel or AMD) can consume 45-140 W and that many CPUs operate at 1.2 V, 1.25 V, etc.
So, assuming a CPU operating at 1.25 V and having TDP of 80 W... it uses 64 Amps (a ...
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How can "purely" electrical circuits emit sound?
Moving membranes or piezoelectric materials obviously produce sound waves, but how can "purely" electrical circuits such as transformers or DCDC choppers (and others) often have an audible noise? Is ...
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Why don't we use GaN transistors everywhere?
There has been a lot of research around GaN transistors, proving that they have a very low on-resistance, low gate-charge and are very effective at high temperatures.
So why are we still mostly ...
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Why do we need so many transistors?
Transistors serve multiple purposes in an electrical circuit, i.e switches, to amplify electronic signals, allowing you to control current etc...
However, I recently read about Moore's law, among ...
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BJT in Reverse Active Mode of Operation
What will happen if for a BJT transistor, it's emitter terminal is treated as collector and collector as emitter in a common emitter amplifier circuit?
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What is this unusual NPN-PNP transistor pair?
I was looking for the datasheet for a transistor I'd discovered during some reverse engineering, a DK52T. Unfortunately I can't find its datasheet, but I found one for the DK52D. See the image below; ...
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Selecting a MOSFET for driving load from logic
I'm looking to drive a magnetic door lock from an Arduino. I've found a question about driving a solenoid from an Arduino, which includes a circuit that looks perfect for this kind of situtation:
...
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What's the difference between field-effect transistors (FETs) marketed as switches vs. amplifiers?
For instance, the J108 JFET is listed as "N-Channel Switch", and the datasheet mentions the RDS on resistance, while the J201 JFET is listed as "N-Channel General Purpose Amplifier" (and the on-...
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How to invert a digital signal
I need a way to invert a digital signal i.e. if the input is high, I want the output to be low and if the input is low I want the output to be high.
I think this can be accomplished with a single ...
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Schottky transistor, Not sure I understand it?
So I've been looking through and going through my Digital Computer Electronics book, and I came to this... It seems so simple and I understand the "point" of it, but I'm not sure I understand exactly ...
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Connect load to collector or emitter of transistor
When setting up a transistor as a switch is there any difference between putting the load on the collector or emitter?
As far as I can see the only difference is in calculating the Vbe i.e. ...
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Darlingtons, MOSFETS, and bipolar junctions
I realize there are dozens upon dozens of kinds of transistors, each used for specific purposes. Sometimes there is great overlap; multiple kinds may work in a given circuit, but at times only a ...
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What is the process of going from machine code to electrically controlling individual transistors? [closed]
For someone who writes software but doesn't have a computer engineering background, the dozens of abstraction layers have always bewildered me.
I know all source code in their most fundamental level ...
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Can you make a CPU out of electronic components drawn by hand on paper?
I explored a lot of literature about paper-based electronics recently, and one particular paper caught my interest: “Handwritten Oxide Electronics on Paper” (DOI: 10.1002/admt.201700009) by Elvira ...
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Is transistor the only electronic component on a CPU?
I have been reading about CPUs recently and came to know that all logical blocks and memory on CPU can be made out of transistors. So is it the only electronic component on CPU?
Edit (Made after ...
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What do the arrows in transistor symbols point to (and from)?
Transistor symbols are often drawn with arrows pointing in one direction or the other, depending on type, like in the following symbols:
But what is the arrow actually pointing at? And from where are ...
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What's the purpose of these two diodes in this circuit?
What's to point of using these two diodes? Can't you just replace them with a resistor?
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How are logic gates created electronically?
So we have AND, NOT, NAND, NOR, OR gates, but how are they created electronically/electrically?
For example, what makes NOT gate reverse the value?
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"Starter Kit for electronics" - What to buy?
I'm going to buy some things for back to the electronic world.
Starting with an Resistor Assorted Kit.
Need to buy some kits containing the most common capacitors and transistors... what to buy???
[...
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How do I make the turn off and turn on time equal in a NPN transistor?
I have a simple NPN switch, see the diagram.
I feed a 100KHz square wave (TTL) to the base of this transistor and it turns on very very fast (a few nSec) but it doesn't turn off as fast, it almost ...
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What is the difference between emitter and collector for BJTs?
the (surely simplistic) model of a bipolar junction transistor one is taught in foundational physics course appears to be symmetric. - So, what is the difference between the collector and the emitter ...
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Why would an AND gate need six transistors?
I'm taking a digital design course, and I've been told that a NAND gate needs four transistors to implement and an AND gate needs six (four for a NAND gate and two for an inverter). That makes sense ...
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Why use two transistors driving LEDs when one would work?
Recently received a small PCB from China with a simple LED driving setup (12v input).
I spent some time probing it out and reverse engineered this schematic;
I'm trying to understand why they ...
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Is MOSFET gate threshold voltage a limit or minimal "Full-on" switching voltage?
I've been shopping for some mosfet transistors, for a starter kit, and noticed listings that state a mosfet is suitable for 5v logic, but the data sheets says Gate Threshold is 1-2v.
4v gated mosfets,...
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Can two BJT transistors work as a full bridge rectifier?
It is known that a BJT transistor looks like two diodes back to back (or head to head). With this in mind, theoretically we should be able to build a full bridge rectifier with 2 BJT transistors, one ...
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Choosing the right transistor for a switching circuit
I want to control a siren speaker (has a built-in driver) with an Arduino.
The siren needs 12V and consumes about 480mA.
The Arduino output pin is 5V and can source 40mA maximum.
I would like to use ...
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How can a high-voltage transistor be in such small packaging?
For example:
STN0214 - Very high voltage NPN power transistor
It is said to accept more than 1 kV between its collector and emitter. It comes in a SOT-223 package (3 pins plus a tab). With a ...
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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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How to calculate the power dissipation in a transistor?
Consider this simple sketch of a circuit, a current source:
I'm not sure how to calculate the power dissipation across the transistor.
I'm taking a class in electronics and have the following ...
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Why does MOSFET pinch-off occur?
This question is about enhanced n-type MOSFETs. From what I understand, an inversion layer is formed underneath the insulating layer below the gate of the MOSFET when a voltage is applied to the gate. ...
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How do I know if which leg is the emitter or the collector? (Transistor)
I'm new to electronics and here's a newbie question that I would like to ask:
How do I know if which leg is the emitter or the collector in a Transistor (For both PNP and NPN) using only an analog ...
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Effect of bootstrapping in amplifier circuit
I am trying to understand this "bootstrap bias" amplifier circuit. The picture below is adapted from the book "Transistor Techniques" by G. J. Ritchie:
This circuit is a ...
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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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When are BJTs used in common base configuration?
BJTs are mostly used in common emitter, sometimes common collector configuration. I rarely see common base. When would you use a BJT in common base? For instance, what parameters are different from ...
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What is the difference between SOT 23 and SOT 23-3 package types?
I am faced with two types of packaging:
SOT 23
SOT 23-3
Is there some difference between them?
Based an article in Wikipedia it seems like there are no differences.
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How do BJT transistors work in a saturated state?
This is what I know about NPN BJTs (Bipolar Junction Transistors):
The Base-Emitter current is amplified HFE times at Collector-Emitter, so that Ice = Ibe * HFE
<...
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