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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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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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Stability factors of a voltage divider bias circuit

I am trying to derive the stability factors of a voltage divider bias circuit. I could derive S,S', however I'm facing some problem with derivation of S''. Please help me in this regard. How to find \...
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How to select a diode for baker clamp?

What are the requirements when selecting a diode for baker clamp circuit? 1- for example, How the reverse leaking current of the diode affects the circuit? can a diode with relatively high reverse ...
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How does a MOSFET conduct in saturation region?

It is a simple question but I could not find a straightforward answer. When a MOSFET enters saturation region, the channel length starts to decrease, and the channel width is the smallest near the ...
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27 views

Way of powering Arduino+GSM Modem+Cam off 5V powerbank

I'm trying to build a circuit, that would turn the Arduino on by a PIR sensor, take the picture by ArduCam, then transfer it onto a webserver. I got the SW site covered by now, so that is not a big ...
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118 views

Mextram Spice Model for Transistor

Where should I look for a Spice Mextram model for commercial transistors, such as the FMMT415? or Should I try a more advanced analog simulation software, incorporating Mextram or similar transistor ...
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design audio amplifier circuit

I wish to design audio amplifier circuit. Hear I use two stage of amplifiers. 1st stage amplifies 100mv to 1.2V peak @ 2KHz. Q1. When I change the frequency to 50Hz output becomes to 210mv peak ...
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105 views

Using Power Good pins for sequencing

I'm trying to figure out a way to use the Power Good outputs of several stages of voltage regulators to sequence and monitor a board powering several FPGAs. I've done this easily before with a ...
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1k views

Piezo Buzzer Driver Circuit

I haven’t used a buzzer before so I have tried to find out as much I could and finally, I am here to clear my few doubts: Few details about my application: Buzzer: AST1240MLTRQ (i was not allowed to ...
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Low Current Consuption on a Voltage Inverter

I'm working with a uC and a Bluetooth Module. I need the lowest current consumption in this project because it is intended to be a mobile device. Thus, I'm using sleep modes on the uC. Now, I've ...
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68 views

CCD output buffer

Reading the KAF-8300 CCD datasheet, I came across what looks like an emitter-follower to buffer the analog video output, see below: Also from the datasheet: Charge presented to the floating ...
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Off load voltage in npn transistor as a switch

There is transistor tutorial on sparkfun.com (https://learn.sparkfun.com/tutorials/transistors/all). I am wondering why there is 1.3 V drop depicted across the LED1 on the picture, since when the base ...
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Switch resistor with n-channel MOSFET not working

So I try to amplify a photodiode signal with an operational amplifier. As I want to amplify two signals (1 for a high-intensity light and 1 for a low-intensity light) I sort of need to design a ...
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55 views

Series BJT transistors with bases connected through a resistor

For an assignment I was given a problem which consists of two BJT transistors, a PNP and an NPN, in series with their bases tied together. simulate this circuit – Schematic created using ...
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Hybrid model of a transistor

Can someone help me to find the hybrid pi model of such transistor configuration? Assume Hfe = 90, the input voltage is applied in series with capacitor C2, (0.082uF) and Vout it from the red dot ...
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51 views

Determining the output resistance of a BJT amplifier

I'm given the following amplifier: (all the transistors have the same characteristics; Early effect is neglected) In order to calculate \$R_{out}\$, we replace the circuit with its small-signal ...
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LEDs driven by GameBoy sound

My circuit does not work as I thought it should and I'm really confused now. What I want? Two LEDs which will pulse to audio LEFT and RIGHT channel separately. And same for display BACKLIGHT, but ...
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55 views

NPN / PNP Sound activated LEDs

I have some RGB LEDs (common anode) and I'd like to control them via sound from my stereo (line level). I'd like to be able to switch the two behaviors of the LEDs from flickering off when the input ...
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Do Germanium BJTs have lower impedance than Silicon BJTs?

What brings this up is the fact that Germanium has a higher electron mobility than Silicon(as well as lower barrier potential) and does that translate to greater admittance(including susceptance)?
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Mosfet Based impulse voltage generator

enter image description here **Details- Mosfet_1 will turn on for 20ms and charge the capacitor C2 and after that, it will turn off. Then the Mosfet_2 will turn on for 3ms with 40kHz frequency and ...
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108 views

Howcome there is current flowing through the gate of this transistor?

I have a few conceptual questions: If there wasn't Rg (Resistor between gate and drain), would Vin = Vout then? For small signal analysis, current can flow through the gate (AC) if there's a voltage ...
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52 views

Improving a SRAM-based memory cell by reducing number of transistors

I'm working on Emulated version of a memory cell. It is a volatile single-bit memory. It uses 4 NAND gates to store one bit. I want to connect several of those memory cells together to create one ...
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27 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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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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How can I find the frequency of oscillation of this sawtooth oscillator circuit?

Simple question: how to find the frequency of oscillation of this circuit? simulate this circuit – Schematic created using CircuitLab My attempt at answering the question is the following: ...
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71 views

ESP8266 shutting down while powering a mosfet only when said mosfet has a high current load

I am working on a small quadcopter based around the ESP8266-12F. I used a trace width calculator for all PCB traces as well as a 100uf tantalum capacitor shared by all motors to ensure low voltage ...
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34 views

finding two drain currents

below I have the following problem along with the circuit's picture My analysis is as follows: for G and D open \begin{equation} I_{D1}=I_{D2}\hspace{10mm}therefore\hspace{10mm}V_{ov1}=\:V_{ov2} \...
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Need fast and exact voltage follower or divider cascade

Intro: I'm designing a makeshift oscilloscope and now need an input cascade for it (it is more fun project for me, rather than industrial-grade tool). The matter is I want to get something faster ...
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110 views

A monostable multivibrator using two NPN transistors works as desired in LTSpice, but in reality is very different

I designed a simple monostable multivibrator to extend a pulse of width \$\approx\$ \$1{\mu}s\$, to \$8ms\$ (to illuminate an LED when something happens on a bus). This is the circuit here, and the ...
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172 views

Peltier Circuit Components

New to electrical in general, so be gentle... Looking to drive a TEC1-12706 as a cooler/heater, using 24V, 500 Hz PWM as input. To avoid thermal cycling caused by PWM, incorporating LC filter. In ...
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52 views

Resistor for transistor base

Inverter Circuit I intend building this circuit however I am limiting the amps (Ice) to 2.5A. Therefore I need the appropriate resistor (R3). I have the following questions: Is the output voltage ...
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61 views

Design of a differential pair

simulate this circuit – Schematic created using CircuitLab Problem: I need to design a differential pair with a gain of 30dB To make this design I have to used 4 mosfets transistor 2n7000 with ...
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191 views

Can you buy Aluminum Nitride transistors?

We all know wide bandgap semiconductors, currently galium nitride and silicon carbide are the superstars becose many companies make them at relatively reasonable price. They aren't just mere lab ...
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Transistor logic to drive h-bridge with negative voltage source

Shown below is a H-Bridge circuit I have used to drive the cathode of a VFD display with a source voltage of +2.4V with a +3.3V digital logic level. I have decided to switch the cathode source ...
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76 views

what is normalized transconductance uesd for?

The transconductance is defined e.g. for BJT by gm = dIc/dVBE with VCE=const (1) where Ic is the collector current and VBE is base-emitter voltage, and from (...
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design of a startup switch

I have made the regulated charge pump of -6V and it will be connected to the PWELL region only. But for the startup case, when we power on the chip we want the charge pump should be 0. I want a ...
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561 views

Replacement for a P-Channel Depletion MOSFET

I've read some of the questions about P-Channel Depletion MOSFETS and I understand their availability is very limited and often expensive. So what I'm hoping to discover with those that view and ...
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What sets the MAG of a BJT?

Suppose you design ideal matching networks on the input and output of your transistor so ALL we're concerned with is the transistor and the packaging. What semiconductor physics or parasitics or ...
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Understanding the operation of HEMT

I am trying to understand the operation of HEMT. I am stuck at the concept on how the electrons gets into the potential well and how its controlled. Here is what I understood till now: In a MESFET, ...
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Identify two National semiconductor transistors 506 220-0075, 452 220-0076

I am trouble shooting a power window amplifier circuit board for a Nissan Quest. The circuit board is relatively small, it has a few active component, most of which can be identified by simply ...
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120 views

Can I control the charge of a Cell-Phone with a 555 Timer and a Transistor?

I want to charge my phone in a controllable manner, using a 555 and a Mosfet transistor. The 555 is a countdown timer that gives an output (pin 3) of 5V for 1 minute, and then remains at 0V until an ...
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163 views

BC109 to Drive a 75Ohms realy

Transistors are always very confusing to me. I read and try to understand the specsheet always but never confident about my understanding :( I have PCB (readymade), which gives me a 2.8V output when I ...
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64 views

Current drop a certain vds in a transistor

I am measuring the I-V characteristics in a transistor using a 2 channel source measurement unit (SMU) when I change the \$V_{ds}\$ and measure the current while connecting the gate and the source to ...
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39 views

make arduino start when a line is broken

simulate this circuit – Schematic created using CircuitLab Hi. I'm trying to build an anti-theft project. Where if you break a thin wire connexion, It should power ON the arduino and let it do ...
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149 views

Intrinsic glitch of the XOR PORT

Good evening, I'm dealing with the glitch of the xor gate. I read on the book 'Code Design for Dependable Systems: Theory and Practical Applications' that a glitch is generated when more than one ...
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201 views

Buck converter welding machine

Can I use a high power (2-6 kw power supply) synchronous buck converter ( at least 85% efficiency) to work as a welding machine that outputs around 10 -20 VDC and 100 -300 amps? If I can, what is the ...
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361 views

Controlling the GND rail

Okay so I'm running into trouble with my small setup, and I'm not sure how to go from here. I've drawn up a very (terrible) schematic of what I currently have wired up: So currently, I have 12v ...
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MOSFET Parameters LTSpice

This is the LTSpice model of the Fairchild 2N7002 NMOS transistor. ...
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337 views

Significant voltage drop across IGBT

I'm using an IGBT in a wireless charger circuit as a swtich to send 'pulses' of power across the gap. I have 14V coming from the mosfet driver and I can see around 5v on the collector. I have the ...
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79 views

Wide Open Throttle transistor switch

I bought a car that had a transmission swap, transmission was a bit lazy so i had it scanned. The transmission ecu is looking for a physical Wide Open Throttle(wot)switch that is grounded when the ...