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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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How to calculate the input and output capacitors of a common emitter amplifier using BJT?

Sorry if the question is stupid, but my head is still hard as a coconut and I am learning... I am dealing with this circuit that I have calculated from scratch. This circuit was designed to have ...
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48 views

battery swapping

I am new to electronics. I am currently trying to create a circuit to swap between 2 battery source when one of it goes flat (1 lithium polymer, 1 lithium ion battery). Is that possible to do so with ...
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75 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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68 views

Help selecting a NPN transistor

Looking to use a relay with ardiuno but having a hard time trying to figure out what transistor I need to use, all the tutorials I can find always use an example transistor (usually 2N2222) to figure ...
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29 views

EDI Meter version 1 [on hold]

Hey can anybody help me figure out exactly what type of transistor I need for my EDI meter? It is the transistor that rests between the top two (red temp) LEDs. It broke out and fell during an ...
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2k views

How do I really calculate these resistors?

I am learning about it. I would like to focus on this circuit I am trying to calculate R10 and R11. I want Ic = 10 mA. Transistor is 2N2222A. This is an amplifier. If I understood how amplifiers ...
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4answers
123 views

Use current from SMD LED to switch larger current

I've got a bluetooth receiver with blue SMD LED's on that flash to indicate connection status. I would like to take that status LED and replace it with the white LED that's in a switch I have. The ...
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2answers
55 views

Totem-pole bipolar circuit explanation

I came across the following circuit in my text book: Summary of the explanation given in my text book: When control input Q3 is low, Q1 is on and output is HI. When control input Q3 is high, Q2 is on ...
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28 views

How to find the input impedance of PNP circuit [on hold]

The early effect is not considered, how to find the input impedance of the circuit shown below?
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27 views

Martin S Roden Problem 5.56

I wanted to see if you could help me with this problem. I have trouble understanding the interactions between the transistors, specially figuring out VC1, VC2, VE1 and VE2. Im attaching my work so far....
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89 views

Understanding the trancitor (transfer capacitor)

In one of my lecture class, one of my electronics professor told a little about a new technology called "trancitor" and told it is opposite of transistor. He asks us to learn more about it on our ...
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128 views

Trouble making a XOR gate with NAND gates

I'm trying to implement a XOR gate using NAND gates but I'm getting a short circuit in the part circled in the diagram. If anyone could help me fix this I'd greatly appreciate it. I made changes as ...
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43 views

Voltage increase on regulator load

I have a simple adjustable power supply (1.8V - 16V / <1A) that I put together with an LM350, works great for the various small bench-top things I use it for. Typically on a load being applied, I ...
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103 views

I am trying to build a 0-42v Voltage measuring circuit that outputs to a 5v Micro! Failing badly

I am on to my next project which doesn't seem to be working as planned. At first I thought that I would find a boatload of pages on how to do this, but to my absolute surprise I couldn't find anything ...
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1answer
62 views

Damaged TPL7407LA Transistor Array

Application We have chosen the Texas Instruments TPL7407LA to drive groups of LEDs for an automotive lighting solution. The TPL7407LA inputs are connected to +12 VDC input signals to trigger the ...
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1answer
55 views

Is pulling current from Collector to Base allowed? (PNP transistor)

I am building a P-Mosfet gate driver and I have a question regarding the behavior of a PNP transistor connected in this way: This circuit might look pointless, but it's a good representation of a ...
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1answer
63 views

What type of transistor is this

I can't seem to find what type of transistor this is based on the markings. It's broken, so I need to replace it. It is in a Chrysler Jeep radio from 1995. The letters are "CBRP". Thanks.
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64 views

Understanding an ultrasonic piezo driver circuit

[Disclaimer: I'm okay-ish with digital electronics, but somewhat a noob with analog stuff. Since this circuit is a) pretty simple and b) still covers both areas, I was hoping that somebody here could ...
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47 views

Transistor as variable resistor in LFO

I've constructed a basic dual op-amp LFO as in the below circuit simulate this circuit – Schematic created using CircuitLab The variable resistor R5 is used to alter the rate of the LFO, I'm ...
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49 views

Transitor Aerial pre-amp for an old valve radio (see edit blow main text) [closed]

Please suggest an available RF transistor type that could operate in MW bands to boost the aerial signal to an old battery valve radio. LT of 3V is available as is an HT of 90V
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36 views

Command Solid State Relay using NPN transistor 2N2222 [duplicate]

I'm trying to command a Solid State Relay with the HV1 pin, I can't connect it directly(HV1 to CH1) due to the fact that the impedance on that pin is too low and I only obtain 2.8V when connected. So,...
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2answers
86 views

How do coupling capacitors in transistor not affect biasing?

I understand the usefulness of the capacitors in an amplifier circuit but i dont understand why we use one at the input? and how does this not affect the biasing if it removes the dc voltage? Thanks.
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41 views

PMOS High Side Switch

I have been working on a project and one of the ideas was to control power supply of LCD 16x2 module and IR sensor via I/O pin of microcontroller, basically to have them on/off when i need them to be. ...
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25 views

Voltage controlled switch simulation

I'm trying to short two pins on a chip when an audio signal is received and float them otherwise (same effect as a tactile switch). I thought the best way would be to use a voltage peak holder and a ...
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1answer
26 views

Confusion with understanding the fixed bias circuit

Below shows a bipolar transistor in fixed current bias configuration. A text says that this topology is independent of β: What I understand is, since Vcc, Vbe and Rb is constant the base current ...
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2answers
37 views

Common collector effect of emitter resistor on output impedance

I've been trying to figure out why the expression for output impedance in a common collector configuration contains a parallel Re emitter resistor. Looking at the classic circuit, it looks as though ...
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37 views

Use an NPN transistor for 12V logic

I want to steer this led strip: aliexpress link With my atmega. Since I will be connecting it to a car, the 12V power will be easily supplied from the OBD2 port directly, but I will need to send data ...
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2answers
103 views

Prevent NPN Transistor Base-Emitter Current

I'm making a simple AND gate array out of 2n2222 transistors. Here is one cell: simulate this circuit – Schematic created using CircuitLab When Input "A", is disabled, and "B" is still on: ...
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7k views

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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88 views

Current Source - MOSFET vs Bipolar NPN/PNP for stability

Consider the schematic below. There are several pro an con for each, I would like to focus here solely on regulation stability. (Not voltage drop or opamp current as this is already answered). I ...
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1answer
69 views

Is there such 555 timer circuit?

I was wondering if there is a simple 555 Timer circuit, or even simple transistors circuit, that has a HIGH output for 1sec, 2sec, or more seconds when I trigger the input switch and will remain HIGH ...
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1answer
64 views

Analysis of BJT transistor - is a linear analysis possible?

Since semiconductors aren't passive components, can I realistically derive analytic solutions for a circuit with BJTs? I know this may seem like a very naive question, but am I on the right track with ...
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59 views

How to calculate the output voltage of the mirror circuit?

Please refer the following circuit added. Output voltage (Vout-A) is measured as follows, Following is the way I have started analysis: Krichhoff's voltage law around the loop ( R12 -> R3 -> V_BE(Q2)...
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42 views

how to adjust drain bias to keep power dissipation constant (HEMT)

I am reading a chapter in a thesis about using HEMT (high electron mobility transistor) as a cryogenic amplifier. The measurement scheme is to use the gate voltage fluctuation's influence on the drain ...
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79 views

Why does a MOSFET enter saturation?

From all my browsing, it has become clear that as drain-source voltage increases, we eventually reach saturation. Mathematically, Vds>Vgs-Vt is the condition we look at. But when I try to understand ...
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54 views

Small signal equivalent circuit - MOSFET

Let's consider the following amplifier circuit: Now, if we would analyze small signal operation, we could represent the circuit with small signal equivalent: The part that bothers me is the PMOS ...
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1answer
39 views

Turn off circuit using microcontroller signal

I want to turn off this circuit using micro controller signal to base of Q4 transistor. Can I use the same transistor model for Q4 as for Q3? I'm attaching the picture of schematic from Proteus ...
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31 views

Transistor for high power application in photovoltaics

I have the following situation, where there is a need for a switch with low conduction losses and controllable variable resistance, to cut-off photovoltaic (PV) panel. The PV panel is in series with ...
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1answer
26 views

-Ve feedback comparator and its threshold values?

I was trying to analyse and understand the following circuit. My intention was to calculate the hysteresis of the comparator. Circuit working: For both compartor input, there will be voltage inputs ...
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2k views

Is it good practice to run large amounts of current through a MOSFET?

I have been looking for a good way to control the flow of a lot of current in my project. This may at some points be 40-50 amperes at 12-15 V. While relays are a good choice, they are mechanical ...
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2answers
83 views

How to determine the most appropriate DC amplification value for a BJT?

The BJT diagram is shown below: The voltage source at the base side is increased incrementally from 1V to 10V, with the voltage source at the collector side being constant. The Beta values are ...
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77 views

Using MOSFET to turn on/off auxillary electronic circuit

I have custom-build e-bike which is basically a motor, battery, controller and an LCD screen with 3 buttons. When I push ignition button, the LCD sets voltage on one of it's signal wires (blue) to 51 -...
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3answers
84 views

Solvng transistor circuit

The transistor circuit in shown in the schematic I have included: simulate this circuit – Schematic created using CircuitLab I have tried solving it like this: First I calculated the ...
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2answers
72 views

How can I control 4 separate Motors from a single H-Bridge?

I have an interesting problem. I am trying to control 4 separate actuators at the same time so they lift at the same speed. Each actuator has feedback and at max draw they pull 12v10A each. The h-...
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2answers
72 views

Exactly what type of resistor is being referred to in this diagram?

I'm trying to control an RGB LED strip using a NodeMCU. I have been following the guide linked here. However, the diagram included in the diagram is rather unclear, especially for someone like myself ...
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4answers
246 views

Switching a divided voltage with transistor or MOSFET

I have a problem that I cannot solve and need help. I have an analogue input on a microcontroller and I want to have multiple switches which the micro can see and act on depending on which switch was ...
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1answer
55 views

Can really small transistors be modeled as in undergrad textbooks?

Most undergrad textbooks on microelectronics (those covering semiconductors, diodes, BJT's, FET's, etc.) that I have laid my hands on discuss semiconductor concepts such as charge carries, drift, ...
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1answer
72 views

Control large voltage supply using smaller voltage

I have a 6 volt supply that I need enable/disable using another 3 volt supply. If I use a PNP Darlington set-up like this: Then I get just under 6 volts at the Output node. My problem is that I don'...
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100 views

Gate of a transistor and mosfet damaged

In my schematic, I found that the base of transistor Q7 (2n2222) was damaged. I tried to replace it with a BS170 MOSFET, and the same thing happened where the gate was damaged. The microcontroller ...
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95 views

How to control 12V from 5V using transistor? [duplicate]

i have used BC547 Transistor to stepup from 4.6v but I can't able to draw above 5v from collector, I have given input of 4.6v to base and emitter to ground and collector to output load. but load doesn'...