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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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Switching ON/OFF an ADC line

which electronic component could one use to switch ON/OFF several external lines for ADC? Context: I am working on a small project where I would like to measure 4 external voltages (0-3V range, let's ...
Bob Becher's user avatar
2 votes
2 answers
53 views

4N25 Optocoupler design

Below is a simple 4N25 optocoupler circuit that I designed in LTspice. 10 mA is flowing through the input. It works in saturation. According to the datasheet in Figure 2 (CTR-sat), it says 0.7, so the ...
Mhan's user avatar
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1 answer
109 views

Why does this transistor amplifier fail if Rc is greater than 50 ohms?

This simple circuit amplifies a 1 µV 50 ohm 7 MHz signal (e.g. RF off an antenna) quite nicely (31 dB): However, I'm stumped as to why R2 must be so low (50 ohms), giving a Ic of close to 50 mA. ...
SRobertJames's user avatar
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2 votes
1 answer
252 views

Is my setup for a 5V motor project faulty?

I'm trying to get a motor (5V nailbrush, no name, no specifications whatsoever) to spin for a set time and pause for a set time using a PIC10F200 microcontroller in conjunction with a 2N2222 NPN ...
I have no enemies's user avatar
6 votes
2 answers
847 views

Will this 3.3 V signal voltage be high enough to close Q3?

3 V signal (PWR-ENABLE) be enough to turn on this circuit? The collector of Q3 will be at 11 V before switching is to occur. Q3 Data sheet Q1 Data sheet
Tim's user avatar
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2 votes
1 answer
61 views

Transistor AND gate problem

I am new to electronics and I built a simple AND gate from 2N2222 transistors. I want to use the output from the AND gate in a different circuits not just an LED but maby an OR gate. Can someone tell ...
RedEndermanSK's user avatar
0 votes
0 answers
29 views

Help Needed: Time Response and Laplace Transform of Transistor Circuit [closed]

I need assistance with solving the following circuit problem. The task involves two main parts: I need help with the following circuit problem: Find the time response of the circuit. Write the Laplace ...
Alon Malka's user avatar
0 votes
3 answers
121 views

Power dissipation in an IC

Here is LM741 op amp circuit in Figure 1. The amplifier has two power supplies \$V_{cc}\$ and -\$V_{ee}\$. The up arrows are connected to the positive power supply \$V_{cc}\$ which is +15 V. Current ...
Amit M's user avatar
  • 701
2 votes
4 answers
309 views

Why is a push-pull transistor configuration asymmetric?

Looking at the circuit below: How do I analyze it? Specifically, why is the output able to go nearly all the way to +12 V but not beneath 0 V? I'd expect that when V(sig) < 0, since current flows ...
SRobertJames's user avatar
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0 answers
22 views

How can I drive a MOSFET with high input capacitance using discrete transistors? [duplicate]

Driving MOSFETS at high frequency is hard, especially if the MOSFET has high input capacitance (as high power MOSFETS typically do). There exist dedicated ICs to drive such MOSFETs. However, for my ...
SRobertJames's user avatar
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3 answers
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How do I analyze an emitter follower with a capacitive load?

How do I analyze an emitter follower with a capacitor load? At 7 MHz, a 1 nF capacitor has impedance of 22 Ω. A simple emitter follower with a 22 Ω Re is easy to analyze: However, replace that ...
SRobertJames's user avatar
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4 votes
4 answers
558 views

Simple BJT circuit problem

This problem is from Transistor circuits and applications by Cowles: Attempt at solution The circuit diagram seems incomplete to me, because they assert a +12 V potential at the emitter but the ...
Carl's user avatar
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0 votes
1 answer
41 views

Identify board components Yaskawa Z1000 VFD

Is there any way to figure out part numbers for the two components from the picture? That's on board of Yaskawa Z1000 VFD.
user388390's user avatar
0 votes
1 answer
73 views

Please help me identify this IC - top marking "CEK"?

Please help me identify this IC - top marking "CEK" such as picture below:
HNLinh's user avatar
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1 vote
1 answer
70 views

Can anone identify this IC marked `55JT`?

Please help me identify the IC pictured below:
HNLinh's user avatar
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0 votes
0 answers
19 views

FD-SOI Channel formation with fully depleted body

In an FD-SOI the body is undoped, which could be just an intrinsic semiconductor such as silicon. What I'm wondering is how the channel is formed in an FD-SOI when the body isn't doped at all. My ...
SalvagedDoor's user avatar
0 votes
1 answer
47 views

Identify IC marking LCSZ

Can everybody help me IC LCSZ such as picture below
HNLinh's user avatar
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-1 votes
1 answer
52 views

SMD transistor identification [closed]

What is value of "HF" as written on an SMD transistor? I think it should be BJT or FET. It is very small and has 3 terminals. Please I honestly need to replace it.
Anietie Udoh's user avatar
2 votes
1 answer
68 views

Why do I have to increase the current by 2V when I am using a transistor?

I have a 3V 3W LED, which I would like to control with an ESP32. For controlling the LED, I have chosen a TP122 transistor. Here is my 'schematic': (The Arduino is an ESP in real life, and the 3 V ...
Marci's user avatar
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2 votes
3 answers
423 views

Why do some JFETs oscillate and others don't?

Below is a simple JFET Clapp Oscillator, which works quite well. It starts oscillating at around 40us and gets into clean, stable oscillation by 100us: When I replace the J309 JFET with a more ...
SRobertJames's user avatar
  • 1,135
1 vote
2 answers
271 views

Solving complex opamp circuits

I'm having some troubles understanding how to solve complex circuits with opamps like the following: During my lab course (I'm a physics major) the professor showed us the solution of very simple ...
deomanu01's user avatar
1 vote
1 answer
51 views

Designing a 24 V output relay using PCF8575

For this project I am using a NUCLEO-F429ZI which interfacing with PCF8575 over I2C. I am operating the PCF8575 only as output. I have tested the PCF with NUCLEO and it works without any issues. But, ...
naman's user avatar
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0 votes
3 answers
85 views

How much current will a BJT transistor draw through its base?

If a BJT transistor has a voltage Vb at its base, its nominal emitter voltage Ve will be Ve = Vb - 0.7. If we know Re, we know the current through the emitter Ie = (Vb - 0.7)/Re. If beta is high, ...
SRobertJames's user avatar
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0 votes
1 answer
106 views

Do transistors "prefer" to pull current from their base or collector?

The circuit below is a simple BJT amplifier which behaves exactly as expected: If I remove the capacitive coupling and voltage divider bias and replace it with an input offset, it completely breaks ...
SRobertJames's user avatar
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0 votes
1 answer
55 views

Help me to identify an SMD component marked 'NM' in an SOT-89 package

Identify transistor marked NM:
Ksm's user avatar
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0 votes
1 answer
64 views

What is the purpose of the diode in this complementary class B amplifier?

For this circuit, why did we use a diode between the bases of the two transistors?
FISqrt's user avatar
  • 161
2 votes
3 answers
215 views

What's the role of the transistor on power input in this schematic?

This is the relevant part of the schematic for ESP32-2432S028 board I have. It's normally powered by 5V over Micro-USB (the right-hand schematic). I want to power it with 5 V through the HC-1.25-4PWT ...
SF.'s user avatar
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2 votes
1 answer
69 views

How to distort a square waveform to get even harmonics?

I'm using a microcontroller with internal 12 bit DAC (buffered output, capable of 0-3.3 V) to produce an analog output consisting of variable amplitude square waves (0-270 mV) at a narrow audio ...
Dimitri Petrucci's user avatar
0 votes
1 answer
56 views

Transistor recommendation needed

I'm looking for suggestions on how to control a DC motor with a transistor and a µC. The input voltage is 15 V DC, and the resistance across the two pins of the motor is 3.3R, so we'll call it 5 amps. ...
Bbb's user avatar
  • 101
1 vote
1 answer
60 views

High side MOSFET driver - transistor design

A simple dc-ac converter in full bridge structure and the structure I created to drive the MOSFETs are given in the diagram below.The output of the converter is working properly. The circuit consists ...
Mhan's user avatar
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0 votes
1 answer
43 views

Guitar pedal mod - trigger button presses from a microcontroller by shorting the switch contacts?

I have a guitar foot-pedal (Boss RC-300) and in order to do a lot of the navigation and configuration of the pedal I have to keep crouching / bending down to change patches or change settings. I would ...
Boloar's user avatar
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1 vote
1 answer
37 views

Circuit design for a timer and relay

I'm designing a timer circuit that detects white cards with black stripes, which needs to be inserted in a specific position to activate. The black stripe sensor must remain disabled when the card is ...
John Madureira's user avatar
10 votes
1 answer
602 views

Why does 2N2222 allow battery current flow when separate 5V circuit unpowered, but 2N3904 doesn't?

To continue my learning on the hardware side of electronics, I built a small circuit with a NE555 precision timer in monostable (one-shot) mode to power a fan for about 30 minutes and then turn off. ...
David C. Rankin's user avatar
0 votes
0 answers
44 views

Homemade Darlington for NEMA 23 motor

I'm demonstrating the recycling of e-waste to my local community by mining and recycling parts from entertainment equipment found in thrift stores. As such, PNP transistors are very hard to come by. I ...
eternalsquire's user avatar
1 vote
1 answer
175 views

How to identify this IC FG97

I'm trying to identify an IC labeled FG97 1847 17145. It is a 16-pin SMD.
HNLinh's user avatar
  • 173
1 vote
2 answers
78 views

How can I find time constant of a RC circuit with a transistor circuit when switch is closed?

First of all maybe this a easy question but I am a beginner, so forgive me. I am having trouble finding the time constant shown in the circuit. How we analyze this?
Yağız's user avatar
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0 votes
1 answer
60 views

Decreasing the input offset voltage of two stage opamp to below \$1 \: \text{mV}\$

I'm working on a two-stage opamp constituted by MOSFET transistors. The important specifications for this project are Open loop bandwidth of \$30 \: \text{MHz}\$ Closed loop gain of \$2\$ A standard ...
Carl's user avatar
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0 votes
0 answers
32 views

Convert PWM negative signal to either On or Off signal

I am trying to make a simple conversion circuit to take a negative PWM signal from my cars dome lamp signal and simply make it or or off. I believe I should be able to use a PNP transistor and ...
Jaxon's user avatar
  • 1
3 votes
5 answers
333 views

How does this gate driver generate 200 V from a 12 V supply?

How does this gate driver generate 200 V from a 12 V supply? And why when off does it never go below 50 V? ...
SRobertJames's user avatar
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1 vote
0 answers
38 views

A transistor latch in dual-supply

I need to build a few latches they are supplied from +rail and -rail. When the latch is ON it should output strong +Vrail and -Vrail also (not through resistor). A solution on picture comes to my mind....
Michal Podmanický's user avatar
0 votes
0 answers
100 views

Designing a 0.18-µm CMOS Multi-Stage MOSFET Amplifier (150 V/V Gain, 1-5 GHz) Without External Resistors/Capacitors

I'm working on a project to design a full-transistor-based (MOSFET) multi-stage amplifier using 0.18-µm CMOS technology. The requirements for the amplifier are as follows: Voltage gain of at least ...
Raczidian's user avatar
0 votes
3 answers
95 views

Finding RθJA for 2N3055

The data sheet does not provide RθJA spec. So how does one go about calculating it?
mike's user avatar
  • 1
0 votes
2 answers
63 views

Darlington control with Op Amp and DAC

The purpose of my circuit is to control(current) a servo motor with the 4096 steps of the DAC MCP4725. Currently this circut is not turning on the NPN Darlington, I don't know why that. The DAC is ...
johnnytolengo's user avatar
0 votes
3 answers
84 views

How can I calculate a transistor's IB, VBB and VEE from the given information? [closed]

I'm new to using transistors, and struggling with a problem that resembles this: As you can see, we have a few known variables: VCC is 5V IE is 20mA There are also some variables with a range: IB ...
Steam Ranger's user avatar
3 votes
3 answers
890 views

How can I use a transistor to control the segments on this 7-segment display?

Pictured here is a 4-digit 7-segment display: Datasheet I'm designing this to have a microcontroller controlling it through a shift register (2, actually). The shift register doesn't have much power ...
Steam Ranger's user avatar
0 votes
2 answers
91 views

Cant figure this out [closed]

Below circuit pulled from homemade-circuit.com, Practical Voltage Regulator Project with Feedback for Enhancing Output Accuracy, https://www.homemade-circuits.com/simple-voltage-regulator-circuits-...
hhsting's user avatar
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3 votes
1 answer
225 views

Using a transistor to digitally press a button

Relatively new to electronics so don’t know all of the terminology, so please excuse me if I express things incorrectly. I have a fan remote that I would like to control using a Raspberry Pi (photo ...
Antheloth's user avatar
  • 133
2 votes
0 answers
65 views

How to calculate the output impedance of a gain-boosted biasing circuit [closed]

I've been working on calculating the output impedance \$R_{Out}\$ ​of the gain-boosted biasing circuit shown in picture, where all transistors are in the saturation region. While I understand the ...
mouin's user avatar
  • 31
3 votes
3 answers
433 views

How to capacitively couple an emitter follower to a load without losing most power?

As an exercise, I'm designing a circuit that takes a 7 MHz input signal (1V amplitude) with a source impedance of 1K and uses it to power a 50 ohm load. I used an emitter follower, and it works well ...
SRobertJames's user avatar
  • 1,135
0 votes
3 answers
103 views

Simple transistor switch does not work

I have a simple switch system based on an NPN transistor (it is supposed to be part of a larger project) which unfortunately does not work and I don't know why. Could someone take a look at what's ...
user3788160's user avatar

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