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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High frequency model of transistor AC ground AC input

When creating the high frequency model for transistor circuits, certain capacitances arise. A lot of them are often in parallel to one another(so they add up) or grounded on both sides(so they get ...
Alema416's user avatar
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How to receive input signal on Raspberry Pi GPIO from transistor emitter

I'm trying to build a simple circuit that allows a Raspberry Pi to detect AC voltage in a piece of wire inductively. I have the following circuit which basically uses an antenna wrapped around the ...
Dyverge's user avatar
4 votes
3 answers
344 views

DC coupled amplifier circuits

How can the transistors in an op amp's differential input turn on if the input voltages are smaller than \$V_{BE}\$, like 0.2V? How can the transistors in the differential amplifier start conducting ...
elt's user avatar
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Controlling 0-5V from 0-3.3V PWM pin and 5V power

What I have is I think a standard problem in home electronics but I can't wrap my head around it. I'd like to control an IKEA light chain from an ESP32 board. The chain is basically a set of LED ...
mariusz's user avatar
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2 answers
208 views

E-Matches ignition circuit

I am currently working on a circuit in order to ignite E-Matches such as these in order to light up the engine of an amateur rocket. In order to have control over when to actually ignite the E-Matches ...
Nick's user avatar
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How to turn on a module with a pulse

I have some issue turning on the module Quectel BG600-ML3. Here are the instructions given in the data sheet : The PWRKEY must be taken high for 500-1000ms. I can only affect the MCU_PWRKEY (Turn on ...
Glantin's user avatar
1 vote
1 answer
295 views

BJT Amplifier Simulation

I am trying to build a simple CE amplifier for an AM signal as part of a home-brewed transistor radio. I would like to have a working simulation before I get a breadboard. My simulation works in small ...
Yousif Alniemi's user avatar
1 vote
1 answer
202 views

Purpose of PNP transistors connected base to base in 1V/Octave synthesizer keyboard circuit

The circuit below (found here) is designed to be used in a 1V/octave keyboard used to control a synthesizer. When the potentiometer is adjusted properly, pressing the buttons produces output voltages ...
dylaneck's user avatar
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381 views

Slayer exciter doesn't work

I know that similar questions have been asked here, but none of the answers seem to work for me. Also, I am new to this site, and I am not much of an expert when it comes to electronics, so feel free ...
ductTapeIsMagic's user avatar
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2 answers
853 views

Switching a load using a 2N2222 transistor with a Wemos d1

So I have this... device... that draws about 0.1~0.2 A and requires 3.6 V. In the below schematic it's represented as a speaker. I want to be able to toggle the power to this device with a Wemos D1 ...
RobIII's user avatar
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Circuitlab - How can I create my own transistor model?

I would like to create some transistors, like the S8050 transistor, for to use in CircuitLab. What I found is https://www.circuitlab.com/docs/custom-device-models/ If I open another existing ...
iPadawan's user avatar
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Why is the depletion layer near the emitter region narrower than the collector region?

While studying Grob's Basic Electronics chapter 28 I came across this statement, Notice in Fig. 28–2 that the EB depletion layer is narrower than the CB depletion layer. The reason for the different ...
Mohsin Raza's user avatar
5 votes
2 answers
4k views

Switch to ground using transistor

I am building an AVR-based diagnostic device for my old Mitsubishi car. To perform diagnostics you must short pin 1 (diag) with pin 4 (ground) on the car diagnostics connector to start a session; no ...
user2120666's user avatar
-1 votes
2 answers
1k views

How do you make a three two-input and gates function as four-input and gate

I'm having a hard time trying to recreate this logic. I used the output of my two and gates connected to another AND gate will that work? or is there any better solution to this problem?
John Nazarene's user avatar
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1 answer
209 views

Electret microphone: convert sound to current or resistance?

See this picture (from Wikipedia): The electret microphone consists of a capacitor with a static charge and a JFET. I wonder how the electrical signal relates to the sound signal. I understand that ...
M lab's user avatar
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What is the name of a two-transistor touch sensor circuit?

I remember a circuit from back in my earlier days of playing with Arduinos and electronics that would light up an LED when two leads are touched with a poor conductor (e.g. a finger). I don't remember ...
shawkins's user avatar
2 votes
2 answers
10k views

Kicad ERC error #3: Power input pin not driven when attached to transistor

The ERC on my schematic keeps on failing due to a Type 3 error (VDD pin of an IC not driven) despite the fact that it does receive power via a voltage regulator and an NPN transistor. See the ...
Neppomuk's user avatar
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BJT: large and small signal models

I am a bit rusty on my BJT circuit analysis and relooking at my college notes I can't remember the cross-over point when you switch between large signal and small signal models. The large signal model ...
Edba's user avatar
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-3 votes
1 answer
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Why are MOSFETs good for audio output?

As title. I read some articles that says MOSFETs are good for audio output transistors and that MOSFETs act like tubes in most case. Here is the article says why it's good: SCIENTIFIC PUBLICATION The ...
Moses's user avatar
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2 votes
1 answer
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Analysis of power amplifier bias circuit: does it need to be thermally bonded?

I'm in the process of building a medium power amplifier for the 20m band (14MHz) and I'm experimenting with bias circuits. The amplifier is a classic BJT push-pull arrangement with a transformer ...
Buck8pe's user avatar
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How to modify the following circuit (using only BC108 transistors) so that two LEDs light up when the motor is moving between position A-B and B-C

I need to modify the circuit included in this post so that one LED lights up when the rotary switch (central left) is set to the middle point, and the motor is running, while another one lights up ...
Peter WG's user avatar
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1 answer
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Is there MOFET with Id is between 10-14A at Vgs<4.2V? [closed]

I am new to the area of working with MOSFETs. For my current project I need a suitable MOSFET or any other transistor, that should work as a switch. My output controlling voltage from controller IC is ...
KUMAR PK's user avatar
1 vote
1 answer
252 views

Is it OK to route under small mosfet transistor?

I have a 2-layer board where I am thinking of routing TX and RX to microcontroller under a small P-channel mosfet. I know some parts can be considered sensitive and one should not route under them. Is ...
mistermister's user avatar
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1 answer
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maximum out put swing question - Transistor [closed]

For example, given two mosfets that have different Vd,sat, but their vout is situated at half the supply range, would it be possible for both transistors to have a maximum output swing? My thinking is ...
Aeden Schmidt's user avatar
2 votes
2 answers
443 views

PNP Astable Multivibrator Variation

I am trying to learn astable multivibrator circuits and I found one in an EL wire driver. I have noticed it has a 100nF ceramic capacitor connected between the transistor bases and additional 22R ...
CDW's user avatar
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1 answer
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Transistor-LED Circuit Design Question

I am using a transistor to drive an LED with a GPIO pin of a microcontroller. Ic is specified to be 25mA I designed the circuit so that Ic can be as high as 100mA before the transistor itself acts as ...
RGB Engineer's user avatar
3 votes
1 answer
254 views

A question related to a NPN transistor having a DC bias

β = current gain I made the circuit of the above picture with LTspice. (A graph of Vce) (A graph of Vbe) And I was able to get 4.2966V for the value of Vce and 0.6543V for the value of Vbe. However, ...
user299980's user avatar
1 vote
2 answers
429 views

Trouble With Transistor (BC547) in Oscillator Circuit

I am brand new to building circuits, so I apologize if I use the incorrect terminology. I am trying to build an oscillator circuit that will output a Triangle Wave and Square Wave in tandem (trying to ...
HustlePuck's user avatar
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1 answer
742 views

Transistor collector current less than base current

What happens if the collector-emitter current is less than the base-emitter current? Do I need to increase the base resistor to lower the base current or is it okay to keep the transitor operating in ...
Lemonbonbon's user avatar
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316 views

Identify SMD transistor - top marking Al PE..?

I need to know the specifications of the transistor that burn out in orange circle on my battery charger. Top markings on 3 other transistors from other 3 working charging circuits seem to be ...
K PC's user avatar
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2 answers
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NPN Transistor Switching - Negative Gain Calculated and Not Switching off Fully = Blown Transistor?

I have the attached NPN transistor being switched by an MCU. I've made some measurements and done my calculations as a result of observing that the NPN is not fully switching off (the relay stays on). ...
RoyalAce's user avatar
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2 answers
601 views

How to make transistor operate in active or saturation-and-cutoff region

There are plenty of quotes on the internet like this one: "There is nothing like 'analog transistor' and 'digital transistor'. A transistor is a transistor! Simple. One can make either analog ...
Doge's user avatar
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2 votes
1 answer
235 views

CCD Horizontal drive diode and transistor selection

I am trying to understand the following part of schematic that is provided for KAI-4011/KAI-4021 Imager Evaluation Board: It is explained by a following description: "The pixel rate CCD clock ...
Ivan Demyachenko's user avatar
3 votes
3 answers
3k views

How to design an amplitude modulator with common-emitter amplifier circuit?

I am facing a problem on how to design an amplitude modulator using a common-emitter amplifier circuit. I am asked to use a carrier frequency of 50MHz and an input signal of 1kHz to 14kHz. In order to ...
Eddy Miner's user avatar
1 vote
0 answers
118 views

how to calculate rx, ro given gx and go from XSPICE

I have a set of XSPICE data extracted from multisim as can be seen in the attached image. How do I calculate the ro and rx (base spreading resistance) given the parameters go and gx. Thanks
Tawseef Patel's user avatar
1 vote
1 answer
2k views

Design a simple transistor amplitude modulator circuit

I saw a simple transistor amplitude modulator circuit on the Internet (image attached below). I have to build a simple amplitude modulator circuit using a transistor for my school project. I ...
Eddy Miner's user avatar
1 vote
3 answers
632 views

How to fix when the amplitude modulated signal reaches the peak, the bottom follows too?

I have designed an amplitude modulation circuit for my school project. I realised that the amplitude modulation can be achieved by just adding a message signal at the emitter part to vary the gain of ...
Eddy Miner's user avatar
1 vote
1 answer
321 views

Problem for 3 mini water pumps controlled by transistors with Esp32 Wemos UNO

Hello everyone I'm doing my project controlling three water mini pump by one board with transistors BC337. The pin will give power when touch sensor sensed something which is embedded in the esp32. ...
Y223an's user avatar
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0 votes
2 answers
135 views

Why the amplifier AB does not amplify the signal?

I have this amplifier AB, but when I measure the signal with the digital oscilloscope, it does not amplify anything, (the yellow one is the output signal, and the blue is the Vin), also when I take ...
Laura Sofía Chanchí's user avatar
1 vote
0 answers
144 views

Improving input impedance at higher frequencies for multi-stage MOSFET amplifier

I am trying to design a three-stage amplifier and I currently have two common source amplifiers and a buffer, to help drive a small 8 ohm load. However, as my frequency increases, my input impedance ...
C T's user avatar
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2 votes
5 answers
813 views

What are the fundamentals behind this p-channel MOSFET / driver circuit?

I have this schematic below. I have a circuit to switch 8 V power using a MOSFET and an NPN transistor with an Arduino's 3.3 V. The power of the switched side will be around 2 A (if this matters ...
Jordan Sheinfeld's user avatar
1 vote
0 answers
81 views

How do I choose currents through my circuit?

Beginner here. I've recently "almost" finished a project in which I am using a relaxation oscillator to get a square wave output with a certain frequency. The circuit works as I wanted but ...
PowerTb321's user avatar
1 vote
1 answer
304 views

Can't understand how the Zener voltage reference works

I've built a small amplifier circuit in which I've wanted to use a Zener diode as a reference but I can't figure out how it works. Knowing that the negative rail is -5V and the Zener breakdown ...
PowerTb321's user avatar
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100 views

Can voltage be increased without coils?

I have a $5 solar lamp. I have recently repaired it. It has a 1.5V rechargeable battery, a small solar panel, a yellow LED, a power switch, a transistor, a diode and some resistors. I am a little ...
zomega's user avatar
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1 vote
1 answer
494 views

How to choose correct resistor values for Colpitts Oscillator

I am having a hard time understanding how to pick resistor values to get the circuit to run. I think I have the basic design down correctly but feel like my resistor values are wrong. I calculated \$...
Geno C's user avatar
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2 answers
455 views

Cut-off frequency of simple transistor circuit with capacitance between input and output

I have the following problem: - simulate this circuit – Schematic created using CircuitLab For the amplifier shown in circuit 1, the open circuit voltage gain at low frequencies was calculated ...
Carl's user avatar
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Converting Normally Closed to Normally Open

I have a truck that has a different engine swapped into it. I'm trying to get the cruise control to work and I've tracked the issue down to the Set/Coast switch. The PCM is expecting a 12 V signal ...
Nick's user avatar
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1 answer
101 views

Schematic review /suggestions: Driving a relay with an Arduino

I am using an Arduino Nano to drive this G5NB-1A-E DC5 relay. My circuit is given below. The BJT (MMSS8050-H) is this one. Is this circuit OK? V_CHIP_REL1_EN is from an Arduino Nano. What things need ...
Hari's user avatar
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Cascade BJT amplifiers gain calculation

I've been trying to cascade BJT amplifier to get a gain of 800. My input is 10 mV, and I want an output of 8 V. My question is, how does the gain of common emitter amplifiers work? I've created a ...
Bottle's user avatar
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How to stabilize this CV triggered toggle (555 timer latching switch) when fed with two gates?

I created the prototype for a modular synthesizer module. The project goal is an AND gate that is fed with two control voltage inputs (A and B with an Vpp around 5V). There will be two outputs: the ...
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