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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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complementary transistor pair npn/pnp in the Kapustinsky circuit

I need to create an old circuit that reproduces fast impulsion, the Kapustinsky circuit (see the picture). This circuit is 33 years old, and a transistor (or equivalent) does not exist anymore, the ...
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Asymmetrical Schmitt trigger circuit

I'm designing a circuit to switch a solenoid with hysteresis. I'd like to switch the solenoid off, shown by R12, when the signal is above 0.8V and switch it back when it's below 0.7V. With the ...
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How does the biasing work in a JFET based triangle to sinewave converter?

To those who haven't see this cool little circuit it employs the non-linearity and symmetry of the JEFET to clip a triangular signal to make it more sinusoidal Can someone please explain to me how ...
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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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56 views

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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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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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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242 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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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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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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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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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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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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Upgraded flipflop square wave generator - did I do good?

I've drawn up a simple multi-frequency square wave generator, based on a astable multivibrator circut, with frequency trimmed by the two ganged pots (both 100k) and the range set by a DPDT switch, ...
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Voltage drop on power bench supply for channel being off

If I measure voltage drop between terminals of my bench power supply (spec) I get -15 mV when channel output is turned off. Why it is not reading 0? I believe it's due to internal impedance of the ...
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What are the differences between the NTE102/103 and NTE102a/103a Germanium transistors?

SO the NTE102/103(a) complementary transistors are a bit more compact(both are cans but the a ones are smaller and thinner). But I've noticed that in particular, the NTE102 is much more prone to ...
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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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48 views

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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Astable multivibrator

I found an Astable multivibrator schematic online and the transistor they used was a NPN 2n2222 and I didn't have one so I was just wondering if it's a must to use a specific NPN or PNP for ...
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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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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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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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58 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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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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54 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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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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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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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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215 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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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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63 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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186 views

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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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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677 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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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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186 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 ...