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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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36 views

What is the least expensive way to build a three-bit shift register?

I'd like to build a queue of three internal bits as inexpensively as possible. Externally, the queue has two input bits and one output bit. The inputs are (dataIn) and (shift), and the output is (...
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1answer
79 views

BJT Clapp Oscilator for 3-6MHz

I designed a Clapp VFO to aid in my Ham Radio projects (Non-superhet SSB and CW recievers for 80M and hopefuly 40M). I chose the clapp topology for it's frequency stability. I want it to tune at least ...
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15 views

Switching 3.3V with a Raspberry Pi gpio pin

I recently bought an IR Camera for my Raspberry Pi, something like this: https://www.amazon.com/kuman-Raspberry-Camera-Module-Supports/dp/B01ICLLOZ8/ref=mp_s_a_1_17?crid=M3FSU2COLT5W&keywords=ir+...
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2answers
44 views

the difference between K coefficient and gm in the mosfet

i know that K in mosfet is as beta in Bjt but since it represents the change in Id in relative to the change in Vgs isn't it supposed to be the transconductance gm ? but why is it different and the ...
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55 views

Using a coin vibrator on a PIC18 MCU

I was wondering how could I add a vibration to a PIC18F45 MCU so that when you touch a key, it would vibrator? I would like to use a dedicated pin from the MCU. Here is an example of a vibrator ...
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44 views

Distortion via Powered Speakers and not in Headphones - 1 Transistor Amplifier

I'm trying to make this NPN amplifier circuit work for my battery powered computer speakers. This circuit works fine if i connect headphones to it in output, but has distortion when connected to a ...
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39 views

Voltage Across NMOS and PMOS Transistors

So I have the question above concerning an NMOS and PMOS transistor. The goal is to find V1 and V2 in steady state. My understanding is that because the gate voltages of zero and Vdd are there, the ...
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1answer
41 views

HFA3096 transistor array breakdown voltage

In the book Learning the Art of Electronics, one of the labs is to build a differential amplifier with a CA3096 transistor array. The author admits that the chip may be difficult to find and gives the ...
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2answers
106 views

Arduino Geiger Counter

I have found somewhere the following scheme for an arduino based geiger counter. (The arduino main purpose is to count the pulses from the tube) As far as I can understand it, the transistor would ...
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1answer
32 views

Feedback on a simple Motion activated motor circuit

I have been working on a Motion activated Motor which uses PIR sensor to detect the motion. The idea is when PIR detects user in front of it motor should start running and when the user moves away ...
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1answer
89 views

What transistor should I use? And how do I determine that?

Im new to designing a circuits. I've got my basic design done. I'm now trying to get to specific parts but I don't know which ones to buy. mainly because I don't know how to determine what I need. I'm ...
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1answer
65 views

Finding the broken cicuit in an Xor Gate

I am new to this particular stack site but I feel that this is the most appropriate place to ask my question. -Background- I've been following an online web course called Nand2Tetris that takes you ...
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1answer
87 views

If npn transistor switch is saturated, does base get galvanically connected to emitter?

Playing with Christmas lamp TRIAC, I got this question. Suppose some transistor is saturated, if gate current is >= 1ma, and I want to control it with 5V Arduino (or STM\PIC\etc) port. So I need to ...
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1answer
19 views

Explanation of Source-Absorption Theorem Example

In the section on the Source-Absorption Theorem, my textbook has the following example: I was wondering: If the voltage $$v_\pi = - v_e,$$ then why do we get $$g_m v_\pi = g_m v_e$$ instead of $$g_m ...
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1answer
99 views

How do actively driven mosfets or transistors react to floating source?

Attempting to add some lights to a car's "intelligent" lighting system. Want to make sure I understand how my n-channel mosfets will react to losing their ground, while their gates are still connected....
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3answers
241 views

Adding Diodes to Transistor Astable Multivibrator; 1N5818 Schottky diodes work but 1N4148 diodes don't; can't figure out why

I am an avid electronics hobbyist, not an electronics engineer. I built a transistor-based astable multivibrator circuit and then fed its output to an op amp buffer amplifier which then drove an 8 ...
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1answer
82 views

Transient Current Effects from Independent Charging Circuit

I've been working to automate a household appliance. The device is normally controlled by a switch that must constantly be depressed in order for the device to operate. Instead, I replaced this ...
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0answers
56 views

Light sensor using transistor

I am trying to create a light sensor circuit using 2N3904 transistor but current is not passing through RL what is error in my circuit?
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2answers
86 views

SPICE BJT simulation results

I'm trying to simulate simple BJT circuits to verify my hand calculations. Following is my circuit, I'm just trying to get the calculated DC collector current with the shown voltages and parameters. ...
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2answers
99 views

How can I sacrifice a bit of DC Voltage to transform it to DC current?

I made a project with using voltage doubler(which has input of 12V) which output is 43V(I expected 24V) but current is low when connecting the 150 ohm resistor,its about 150mA,but I dont need so much ...
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1answer
91 views

Interrupt PWM signal with transistor

Can a transistor be used to interrupt a signal? I know a common use is to switch power to another device. But my question is if I have a PWM signal applied to the emitter and the base pulled up, will ...
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25 views

Non ideal behaviour of a current mirror

Voltage across emitter and collector of QA is 0.7V. In a current mirror, why is it such that when the voltage across the collector and emitter is different for Qb than QA the value of Iout increases ...
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Transistor to safely connect 2 circuits failsafe

A simple project turning into a head scratcher for me. Charging Lipo batteries from 1,2 and 4 cell requires different connector types unless I can simplify an auto sensing connection. I need to ...
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0answers
22 views

Arduino PWM & MOSFET successfully control LED but not electromagnet? [duplicate]

I've got an Arduino circuit set-up so I can control the strength of an electromagnet using a potentiometer. My potentiometer is hooked to A0, and I'm mapping its value to PWM pin 3 which then goes to ...
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1answer
57 views

Unexpectedly high voltage drop in the transistor

I'm driving an LED with a microcontroller through a transistor with a PWM signal. When the gate is grounded, no current flows, as expected. As soon as I start to drive the transistor (1% duty cycle), ...
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1answer
67 views

Current-limit circuit for 78XX voltage regulators

I need to find the value of Rsc and R1 in the following circuit: In this circuit, Q1 is the high-current pass transistor. Its emitter-to-base resistor has been chosen to turn it on at a given load ...
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2answers
703 views

How does this circuit given with diode works different from the standard current mirror circuit or will it work in the same way? [duplicate]

This question had already been asked here by someone else few years ago but I could not see any satisfactory answer so I am asking it again. All I can see relevant in that post was the image attached ...
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3answers
88 views

Is base-emitter voltage of BJT transistor (common emitter configuration) constant?

For sillicon the value of Vbe is approximately 0.7 V. So why is the input characteristics of such a transistor like this Why not a straight vertical line. Or is this curve plotted for I Vs Vbb. I ...
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0answers
91 views

Why do I have voltage on Collector and Emitter when NPN transistor turns on? How to get rid of it?

I have a 2N3904 NPN transistor. I'm feeding the base 5V. the transistor turns on just fine and it shorts the collector and emitter. However, when I turn my meter on volts, I read around 1- 1.5 volts ...
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4answers
78 views

Will switching a LED on and off at a said frequency reduce or increase heat loss?

In my case, a 50W 34V LED is being used to light a small box. To reduce heat generated by the LED, we are switching it on and off at 50Hz. But I was wondering will this actually help? In the case of ...
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2answers
91 views

Transistor KSP44 with Ic(max) 300mA can I use it for 150mA

I have some problems to understand the datasheet of the transistor KSP44 (and transistor in general). I need to control a LED strip. I want to switch it up through a transistor NPN. My transistor ...
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2answers
460 views

LEDs in Parallel; Which Transistor, and do I Need Resistors?

perhaps you can help out. So, I'm making a prop replica and light is a big part of it. To this end, I picked up three cheap LED torches, which have arrays of 9 LEDs in each. Cheaper than I could buy ...
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3answers
99 views

Current Source Output Does Not Become 0

I put a simple current source on a circuit to drive a UV LED with a constant current. According to the LTSpice simulation setting 0 V at the signal input results in 0 A through the LED. But when I ...
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2answers
27k views

How are microscopic transistors on microchips made?

How is something like a microchip which is already small as it is able to house even smaller transistors in the millions at such a micro-scale? It seems like such a feat for machine to be able to make ...
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2answers
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How do I connect a relay and transistor to an Arduino?

Ok, so this is what my relay looks like. I can't figure out what pins I hook the arduino and transistor to, and what pins to hook the the other device. Please help.
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1answer
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OpAmp vs. Transistor [closed]

I have heard that Op-amps are like special transistors with none of the drawbacks and all of the advantages. What properties make an operational amplifier a "better" amplifier then a biased transistor,...
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30 views

Current capabilities of P-Channel Mosfet Circuit

I don't know how to ask the right question it would appear, but the following answer by Dave Tweed Refers: Floating Voltage to Bias a P-Channel Mosfet without Exceeding Source-Gate Max Voltage In ...
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5answers
126 views

PNP transistor turns on at 3.3v

I have connected a 3906 PNP transistor base to a GPIO pin of ESP32 board. Emitter is connected to 5v and collector is connected to a buzzer. When I program the buzzer (send a HIGH from ESP32), it is ...
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2answers
3k views

PIR sensor led strip with N channel mosftet

I have a PIR sensor (HC-SR501) and I want it to turn an led strip(12V 0.8A) on when the sensor detects motion and off when there's no motion. I checked a previous thread which is similar in that ...
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3answers
58 views

Help with making sure a correct use of a BJT

I'm designing a PCB that receives 3 power inputs 3.3v, 5v and 12v. I need simple way to switch all of them of in one go. Here is a schematic of my PCB My 12V line is for running a ws2815 led strip ...
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1answer
105 views

Need to make this circuit with a different transistor

I need to make this circuit with a BC337 transistor, but I'm not sure if I need to change the resistor or capacitor values. If I do, could you tell me how you came to that conclusion. The circuit is ...
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0answers
82 views

CE/CB BJT Amplifier(s) + Load Lines!

This diagram from a lab assignment is not making sense to me...any help would be greatly appreciated. I don't understand what \$I_{C_\max}\cdot R_e\$ is and why it appears on this diagram. Even if it ...
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1answer
106 views

Common collector - bias resistor?

[Original question: CCD output buffer; seemed best to make the transistor part a separate post] Taken from Wikipedia, the circuit in Fig. 1 acts as a common collector (high input impedance - low ...
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1answer
74 views

How do I choose the power rating of resistors in audio power amplifier?

I read a bit about audio power amplifiers and struggle to understand the power rating of the emitter (i.e. current sharing) resistors in power amplifiers. I refer to this project. [EDIT: schematics ...
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0answers
41 views

Determining suitable transistor for replacement

I found a transistor is burned and I am trying to find a replacement one. Though searching with the markings on it, I could not find anything at several electronics shops I tried. How do I select the ...
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2answers
1k views

How do you control 130-size DC motors with an Arduino (seemingly 20A DC motors)?

I'm a little confused on specifications and limitations here... I have 3 (130-size, I believe) DC motors I'm attempting to control with an Arduino. They are running off of a 7.2V NiMH battery pack, ...
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2answers
98 views

Add tilt switch to this photodiode circuit

I'd like to take this phototransistor switch circuit: And add a tilt-ball or similar switch in series. That switch needs to be heavily debounced, so that it stays "switched" more or less for several ...
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2answers
220 views

PCF8575 woes (driving a ULN2803)

Using this shecmatic to drive some relays - works fione for a while then the relays start misbhaving. I'm a moron - the PCF is current based output thingy not a simple "heres 5v or 0v" for the ULN to ...
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1answer
150 views

What's wrong with this single-transistor level-shifter?

I was trying to step up the output of a 3.3V microcontroller pin to 5V for communication with another device. I wanted to do it with a single bjt, and found a good design for doing that here Single ...
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2answers
88 views

Darlington pair [closed]

Here, the first transistor t1, is to be connected in CC configuration. Doesn't that mean that the collector of the first transistor should be grounded? Also, the collector doesn't seem to be "common"...