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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How to calculate currents and voltages with transistors circuit

I'm reading the Art of electronics and trying to calculate current and voltages of the following scheme: simulate this circuit – Schematic created using CircuitLab I wrote the current as ...
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1answer
94 views

“General Purpose” Current Limiter?

So i have been trying for a few weeks to create a current limiter that fills my needs but i have failed/i don't even know if it's possible. Basically i want to make a current limiter that can work ...
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3answers
177 views

How does a transistor behave when the gate is disconnected?

On an n-type transistor, if a voltage above a certain threshold is applied to the gate, current can flow from source to drain. On a p-type transistor, if a voltage below a certain threshold is ...
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1answer
54 views

DC Motor Power Amplifier issue

i built this DC motor power amplifier to drive the motor in both directions using an analog signal (from -1 volt to 1 volt via the potentiometer ) , the motor i use is rated for 24 volts and draws ...
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1answer
40 views

Body interference in my analog multiplexer, maybe AC electromagnetism induction?

I just wired a CD74HC4067 analog/digital multiplexer to a matrix of leds. The multiplexer is wired to control the LEDs, and is connected to an arduino board, which is connected via USB to my macbook ...
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1answer
69 views

Low voltage drop regulators?

I am building a battery backup system for a dc appliance that runs on 6v. I have a 6v sealed lead acid battery to serve as the backup source. However i read that a lead acid battery at full charge ...
4
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1answer
93 views

Transistor PWM Generator (No ICs) for practical application

I want to produce a good quality PWM signal with transistors(BJTs, FETS, etc..). I do not want to use an IC at all(learning to use transistors properly). I'm currently using a BJT Astable Mutivibrator ...
0
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2answers
110 views

which transistor to use and how [closed]

I would like to use a transistor in my circuit to cut off power. My power supply gives out 12v @15 amps. I think in this case I'll use a npn transistor. Which kind of transistor can sustain this ...
0
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1answer
49 views

I made a fluctuating circuit that controls an LED to be on or off, How does it work? [duplicate]

I have this circuit, The two ends represent the positive and negative terminals of the battery. Values R6-4.7K R1-470K R2-470K R3-4.7K C1-.1 uf C2-.1 uf All ...
0
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3answers
74 views

PNP transistor instead of mosfet to register small clock and data signals [closed]

I have a device that outputs -0.2v clock and data pulse (It works on CR2032 (3v) and I assume it's CMOS), I want to register that signals on arduino in simpliest way. Since no mosfets have threshold ...
3
votes
2answers
88 views

Why do we have 2 representations for load (shown below) in a power amplifier?

OR I get confused when i see two different ways to connect load resistor in a power amplifier. Why do we have two such representations (RL in series with collecor Vs RL connected across collector ...
3
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1answer
427 views

Propagation speed of telegraph signals

Time transfer in the late 19th c was best achieved by telegraph, a major improvement in the determination of longitude for geodetic surveying. A question was posed, to acquire a high accuracy time, by ...
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1answer
50 views

Applications of transistor feedback

I saw the following circuit in an electronics exam. I think the feedback network consists of a transistor (M3) and a resistor (Rf) and the feedback type is current-current; Is this analysis correct? ...
0
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1answer
59 views

Electromagnet Circuit

I'm working on a small project to power a magnetic lock that deactivates when a series of switches are turned on. I've re-designed my circuit based on help from another post, but isn't supplying the ...
0
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4answers
98 views

Control 5v relay through 3.3v GPIO using NPN transistor

I'm not very pratical as I just started learning electronics and I'm planning to make some experiment with Raspberry Pi. I'm trying to control a 5v relay board that, I think, is made for Arduino, as ...
0
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0answers
30 views

led strip dimmer using potentiometer with switch built-in

I have made a dimmer for a small led strip with arduino and a potentiometer. see schematic below. the 12v are taken down to 5v with a buck module to feed both arduino and the pot. So arduino reads ...
3
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1answer
112 views

Help understanding a 30 year old schematic for a contact aligner

I got this old contact aligner I want to fix up but it is missing the control box, this is the diagram which is from like 30 years ago. Any suggestions on how to interpret this? J2 and J3 are the main ...
0
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1answer
38 views

How to make inverse switch with bc547?

I want to make a circuit where the power to mcu switches from mains transformer to dc battery when when mains power is not available. The basic concept is to use a transistor to stay open circuit to ...
0
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1answer
37 views

voltage selector circuit for programming microcontrollers

I have a microcontroller that has a VPP pin which requires 12 volts to enable programming mode, 5 volts for normal mode, and 0 volts for reset, and I want to achieve all these modes without manually ...
0
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1answer
81 views

Step up SMPS with unrealistic voltage output with a 100W LED COB load

I got some 100W LEDs to make a lamp, realized with a boost converter I could use an old ATX power supply and bingo I'd be fine. It worked at first, until I didn't like the color so I decided to ...
3
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0answers
68 views

Electric circuit diagram proof check - simple

im completly new in this subject (electronics, i began today) and therefor quite the newcomer and would like to know if i understood the use of transistors and capacitors and the diagram in a whole. ...
6
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2answers
1k views

Can I replace multiple NPN transistors with some kind of IC?

I am currently using BC 547 transistor and an Arduino Uno to turn a low power switch on and off. I have successfully achieved this with one of the Arduino output pins, but would like to replicate this ...
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1answer
93 views

Switching on and off high 50V DC circuit?

I'm having a little trouble finding a way to activate my circuit. I don't have a proper circuit drawing tool available however hopefully my drawing from MS Paint will do. //////////////////////////...
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2answers
132 views

How do changes in α affect β for a BJT?

Show that for a transistor with α close to unity, if α changes by a small per-unit amount (Δα / α), the corresponding per-unit change in β is given approximately by $$\frac{\Delta\beta}{\beta}\...
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4answers
284 views

NPN Transistor not working

I do not understand why no current flows through my circuit. This question seems closest to my problem, but I am still having issues. I have tried two different transistors to make sure the issue was ...
2
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1answer
34 views

In MOSFETs why is the gate-body inversion layer voltage able to create a conducting channel, yet the same source-drain voltage not?

I have very little experience with electrical engineering, so please bear with me. I was hoping to get a qualitative explanation as well as pointers to the maths/formulas which could formally explain ...
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2answers
872 views

I was explaining a transistor to someone, and I realized: I don't really understand several key concepts at a low level. Help?

(Surplus story removed.) I was explaining MOSFETs, CMOS, and logic gates to someone and realized I didn't grasp some concepts as well as I thought. It culminated when he drew a single transistor, ...
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2answers
40 views

Limiting resistor for zener voltage regulator driven by transistor

I have this circuit: simulate this circuit – Schematic created using CircuitLab And I would like to understand why I need a limiting resistor for the current flowing through D1. I know ...
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1answer
87 views

How to calculate the transconductance of this circuit?

I have this circuit where the "FES" blocks are simple current mirrors and the block "PD" is a differential pair. All the transistors in those blocks are BJT, NPN or PNP, respectively. I found all ...
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2answers
176 views

Why does voltage go in one direction and not both?

Hello I have this inverter circuit I made that is connected to a button when the button is on one led is on and the other is off and vice-versa. simulate this circuit – Schematic created ...
0
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1answer
29 views

Transistor switch for VFD tube grid

I am designing a on/off switch for the grid of a VFD tube, and I would like to use a NPN transistor. The requirements are: The Grid is on when 12V are applied. At this voltage, 0.85mA flow. I want ...
0
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1answer
124 views

Transistor D-latch does not latch

Hello I have built a d latch using 4 NAND gates and an inverter made from transistors. Here is the schematic. For some reason the latch does not remember its previous input like it is suppose to do....
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1answer
84 views

Simulating a 'shift key' without using relays

It's been years since I worked day to day with electronics and I am slowly coming back to the hobby. This is a question related to an intersection of my hobbies though: arcade stick modding and ...
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4answers
815 views

Do power MOSFETs have significant disadvantages over normal MOSFETs?

I have noticed that many power MOSFETs are cheaper, have a much greater \$I_{D}\$ and \$V_{DS}\$, and have comparable \$R_{DS(on)}\$ and \$V_{GS(th)}\$ values to normal MOSFETs amongst other ...
2
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1answer
43 views

Is the bulk output deliberately used in DRAM cells?

Regarding the structure of a DRAM cell with a MOSFET and a capacity, why does activating the word-line make the transistor connect through? As I learnt, the MOSFET becomes conducting if UGS >> ...
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0answers
30 views

Choosing mosfet replacement [duplicate]

I have Kai Deng K70c quadcopter and recently I burned one of the mosfets. The mosfet is a Fnk06n02d 20v N-channel TO-252-2L. Can you help me choose a replacement?
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1answer
33 views

Relationship of the base resistor and the collector resistor in turning on / off a 12V load with 5V using a transistor

I am testing a solution to turn on / off a 12V load (the load will be MOSFET for controlling DC Motor) using 5V input with a transistor (see attached file for the schematic and the test results). My ...
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0answers
24 views

Board for NEC LD-8035E VFD Tube

A couple of weeks ago I was visiting an eletronic exhibition, and I came home with five NEC LD-8035E VFD Tubes. They look like this: Being my first "date" with a VFD tube (and with a tube at all) I ...
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1answer
81 views

How to choose the transistor and the resistors connected to it [duplicate]

I am using the regulator TL497 in the case of I(pk)>500mA so I need an external transistor for that but in the datasheet they don't mention how to choose the transistor and its resistors does anyone ...
4
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2answers
190 views

what is the tempreture at which the thermal limit of an amplifier is reached

Introduction: I am upgrading a "power amplifier" that a fellow engineer has designed , my job is to add thermal protection against failure in prolonged use (or operator miss use). The package of ...
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0answers
80 views

Queries regarding Digital power supply design

I was designing a 0-35v/6A power supply with keypad entry with microcontroller.The main idea is to output calculated output voltage by a 12 bit DAC and feed it to an op-amp configured as non inverting ...
1
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1answer
56 views

What type of FinFET is this? It is an example file of Sentaurus TCAD

As as I am totally new to TCAD software, I'm unable to parse the code. My doubts are as follows: 1) Whether it is a SOI Finfet? 2) Why am I only able to see half structure at the last node? ...
0
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0answers
69 views

Audio POT with FET and PWM

I've been trying to build a simple audio pot to be controlled with PWM with an arduino, but I'm not sure why it doesn't work. I could do it with a LED (not directly which is simple, but with a FET), ...
0
votes
2answers
85 views

Floating Collector

I am working on a project where power to the 5VDC supply to a micro can be interrupted during operation (by user). I need to signify to the micro that it is about to lose power so it can perform ...
2
votes
2answers
173 views

The Art of Electronics, figure 2.10B

I'm trying to learn electronics and right now I'm reading the book The Art of Electronics. I'm stuck on this chapter 2 on figure 2.10B. In particular I'm simply confused with the lingo like "...
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3answers
81 views

Sedra and Smith Microelectronics 7th edition Example 6.12

I quote from the book: "By examining the circuit, we conclude that the two transistors Q1 and Q2 cannot be simultaneously conducting. Thus if Q1 is on, Q2 will be off, and vice versa." Assume β = 100....
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1answer
134 views

Decoding Transformer circuit for power supply generation

I am referring below schematic of transformer to generate power supplies in the system. Transformer used is step up transformer (Input-5V, Output: +/- 12V, +/- 48) But I am not getting how ...
0
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1answer
110 views

Designing Discrete differential inputs Amplifier [closed]

I am trying to analyse a discrete differential amplifier circuit by answering some question. I have done the analysis of the input stage, I would appreciate if I can get some feedback on my approach. ...
3
votes
2answers
65 views

Multi level logic in transistor level. Possible?

I am currently studying the MOSFET transistor for Digital CMOS IC design. There, the noise ratio is defined and the 50% margin is assigned for a logic HIGH and LOW. Taking the noise into account, do ...
0
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2answers
70 views

Correct resistance for a transistor?

How do you know what R1 should be to completely turn on the transistor? simulate this circuit – Schematic created using CircuitLab