BJT stands for Bipolar Junction Transistor. It is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications.

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NPN BJT non-inverting simple amplifier [on hold]

How to use an NPN BJT as a non-inverting amplifier with a pull-down resistor? (as opposed to using it as in textbooks as an inverting amplifier with a pull up resistor)
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Sedra and Smith Microelectronics 7th edition Example 6.12

I quote from the book: "By examining the circuit, we conclude that the two transistors Q1 and Q2 cannot be simultaneously conducting. Thus if Q1 is on, Q2 will be off, and vice versa." Assume β = 100....
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Negative base current in NPN BJT

What happens if the base current goes out of the base of an NPN BJT?
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Using a schottky diode to improve PNP transistor turn off time

I was able to use the following schematic to improve the turn off time of a NPN transistor Adding a schottky diode (even externally to transistor) component reduces the turn off time dramatically. ...
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What is the advantage that Voltage biased has over the current biased BJT Common Emitter Amplifiers? [closed]

I would like to know the difference b/w the Voltage biased and current biased BJT Common Emitter Amplifier and their advantage sand uses? And can't a transformer be used for biasing? ANd base biasing, ...
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289 views

What's the differences of these usage of PNP, NPN transistors?

I am reading the book Electrical Engineering 101. When talking about NPN and PNP transistors, the book said this: Use an NPN to switch a ground leg and a PNP to switch a Vcc leg. This might ...
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62 views

How to simulate BJT cut-off in SPICE

In BJTs, when applying the parameter of collector and base current cut-offs, everything below a given cut-off current gets floored to 0mA, right? So say if we have a configuration with good voltages (...
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167 views

Implementation of a 8-to-256 decoder using BJTs

I'm designing an 8-to-256 decoder for an SRAM module I'm building for an home-made 8-bit BJT computer. This is what I've got, which is the straightforward and trivial way: However, the design ...
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80 views

High side switching

I have designed a BJT based switch to enable and disable one or more loads with a microcontroller pin. The situation is the following: The controller pins work with 3.3V The devices require 12V to ...
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83 views

Current Amplifier using bjt [duplicate]

The output current through V5 is supposed to be 1A and I am getting around 460μA. TIP122 and TIP127 have minimum current gain of 1000. So the current entering each darlington transistor should be ...
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56 views

Why does the collector current direction remain the same in saturation and active region?

The collector current direction remains same in both active and saturation state where the former puts the base collector junction reverse biased and the latter puts the base collector junction ...
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110 views

Electronic switch with negative and positive voltage

I want to use a micro-controller to send data through a max232 that will convert the 0v/5v signals into -12/+12v signals. The problem with this IC is that when there's no signal, it sends a +12v ...
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MOSFET Replacement for PNP BJT in a 12V switching circuit

I used a PNP to control 12V in circuit. as follows System_Load/2 is 12V DC, MIC1_PWR is the output and LCD_W2/1 is the control signal. This circuit would work fine if the control signal's High is ...
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21 views

Finding thevenin voltage in a common emittor circuit

simulate this circuit – Schematic created using CircuitLab β=100, Vbe(on)=0,7, VA= ∞ Lower corner frequency is what actually wanted. In the solutions of the book, it began with finding ...
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42 views

Base resistance in Tee Model

This is about the 'TEE' Model in BJT small signal analysis on CB configuration. During the lectures, the one I learn is this model; But in some books I found a different model with a base ...
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193 views

How to convert 700V AC to 5V DC 500mA?

I have a device that requires approximately 500 mA at 5 VDC, and I am required to get this power from two legs of a three phase power supply. The voltage between these legs can be between 110 and 700 ...
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51 views

small signal equivalent circuit with BJT and MOSFET problem

Here's my problem. i've been trying to draw the small signal equivalent circuit. And this is what i have but i feel something's wrong because when i calculate voltage gain i dont have to use gm ...
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72 views

P-channel MOSFET with variable resistance on the drain

I would like to switch a variable resistance using a P-channel MOSFET as a high-side switch. I asked a similar question here using PNP BJT; however, it appears as though a BJT would be inappropriate ...
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95 views

Small signal equivalent circuit BJT question

This circuit is two BJT transistors in so called 'darlington configuration'. I want to analyse this circuit for AC signals (where the capacitors are shorts). The question is to calculate Delta_V_L/...
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77 views

h-bridge voltage readings using bipolar junction transistor

I am using the following h-bridge setup using optocouplers, a DC motor and bipolar junction transistors (2N3904 for the NPN and 2N3906 for the PNP) Everything works as expected, but my question has ...
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67 views

Why are the collector and emitter on this TO-92 transistor reversed?

Every TO-92 BJT I've ever seen reads collector-base-emitter when read left-to-right facing the flat side. Then I found this lovely part, BC517. It reads emitter-base-collector. Have I only been ...
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Plot of Ic and Vbe function

The book page 12 show the plot of collector current Ic vs temperature at fixed Vbe =600mV. With the equation: Ic = Is*e^(Vbe/VT). Where Is = 10^-16A. Vbe = 0.6V VT = kT/q = -8.6173324×10−5*T (...
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Why is BJT called as current controlled current source and FET as voltage controlled? [duplicate]

If BJT amplifies only current then why CB configuration has voltage gain but no current gain?
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How is High Precision in Op-amps based in BJT accomplished?

With BJTs there is always an associated Vbe. So when designing with them and taking output from emitter, I simply add a tiny offset so the signal lower than Vbe won't be clipped below ground, then ...
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Small circuit analysis on Common Emitter with bypass capacitor

I'm really not sure how to approach the C2 capacitor in this case, I'm sure it's easier than it seems! I'm not sure about how C2 would affect R5 when performing small signal analysis, would R5 just ...
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Athena: How do I add an electrode on the side

I am creating a bipolar junction transistor with Athena (part of the Silvaco suite). I have to attach an aluminium electrode on the side, with a specific range of y values. I know how to add them to ...
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Unsaturated BJT

I'm struggling for an answer to part (c), I can do the first two questions. I know that \$i_C = \beta \times i_B\$, however, I don't know how to calculate the maximum current gain of the unsaturated ...
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Analog circuit design(amplifier with BJT) with abstraction(model)

I tried to cascade two circuit consisting of BJT transistor : Common Emitter stage, Emitter follower. I do abstraction like belows, which means you just need to know only each unit block one by one ...
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Can any BJT be used for temperature sensing?

I'm looking for a cheap and easy way to monitor temperatures and came across the Microchip EMC1403 which interfaces to general purpose diodes (or transistors with their base tied to collector/emitter ...
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BJTs drawing collector current from a limited current source

simulate this circuit – Schematic created using CircuitLab Let's make everything ideal by ignoring the voltage drops: Q1's allowed collector current is: 22.4 mA Q2's allowed collector current ...
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Common Emitter BJT configuration: output characteristics

Can someone please explain to me why the curve shifts up when there is an increase in the base current Ib ?
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37 views

AC equivalent circuit -BJT

For the following circuit, I'm asked to give the AC equivalent circuit for small alternative signals. On the second circuit (the one they gave us as a solution), I don't understand why they didn't ...
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BJT Common Emitter Positive Power Gain [closed]

I am trying to complete a simple amplifier project using a single transistor common emitter amplifier. I understand that the common emitter is inverting but I need the power gain to be positive. The ...
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Why would I use 2N3904 instead of 2N4401?

2N3904 and 2N4401 appear to be very comparable parts in all specs. 2N4401 has a higher current rating, but otherwise they look to be about the same in price and everything else. Obviously it's ...
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48 views

Common Emitter amplifier Bias Circuit Simplification

This is a slide from one of my semiconductor devices lectures. I understand how the bias circuit works and how to calculate the resistor values however I do not understand how this simplification ...
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How was saturation current found? Was it assumed in this question?

I'm just a really confused about how Saturation current, Is, was either solved/derived or assumed?? Please see images of question and solution. The question requires that you find all the bias ...
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BJT Capacitance at RF limmitations

I am trying to design a simple RF signal buffer using a MPSH10 BJT transistor. This is to operate at ~90MHZ and simply buffer an input RF signal to lower the out impedance of my oscillator which feeds ...
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Drawback of RF BJTs

So when manufacturers build transistors they always have to trade-off certain parameters for others. RF transistors often have a high gain-bandwith product and low capacitance to make the gbw usable. ...
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BJT gain.Width of base region vs collector current

We know that in active region Ic=beta(Ib),so it means that as Ib decreases the Ic should decrease proportionally,but the early effect states that as we increase Vce the width of the base region ...
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LC Oscillator Gain Compression

I am designing an LC Colpits common base Oscillator for the FM broadcast band. The project is going to be extremely low radiated power as I will only be using it in my car. I am currently using this ...
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Must both transistors in a class AB amplifier push-pull pair need to be matched?

A in push pull pair the emitter of the two transistors are connected together. Therefore, what difference would it make if they are not matched vs if they are matched i.e they have same beta value.
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Bipolar Transistors polarity

I have circuits problem where one part specifies that Vb is chosen such to forward bias the base collector junction by .2V. This tells me that Vb > Vc. With the information given I know that Vbc=.2 ...
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How to work out (Hie) input impedance for ZTX650 BJT Transistor?

Please can someone tell me how I can work out hie (COMMON EMMITTER MODE) for ZTX650 BJT Transistor. It is not anywhere on the data sheet. From all the research I have done, one website has told me hie ...
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53 views

Audio Amplifier Design (CE Amplifier - Class AB Power Amplifier)

I am trying to design a Audio Amplifier which provides a gain of 20db (10V/V). I have managed to design the following circuit but the output voltage gets clipped and clamped. Please find the schematic ...
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CE Amplifier Design for Audio Amplifier

I am trying to design an audio amplifier which provides a maximum gain of 20dB (or) 10V/V . For the circuit I designed the lower half of the amplified signal is being clipped. I am also attaching the ...
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1answer
32 views

How to work out (Hfe) AC Forward current transfer ratio for ZTX650 BJT Transistor?

Please can someone suggest to me how to work out the AC Forward current transfer ratio for this BJT Transistor (ZTX650 BJT Transistor) used in common emitter. I looked on the data sheet (herewith is ...
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Question about amplifier design

I'm somewhat new to analog circuit design, and I have some questions about this circuit, which I came up with trying to understand how transistor amplifiers work: simulate this circuit – ...
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57 views

LED switch with externally controlled current from sinking output

My device has sinking output (Vcc=3.3V), the LED current (and voltage) is controlled by another device (a voltage controlled constant current source) as indicated at VLED. The LED IV curves (as ...
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50 views

pwm amplifier with npn bjt

I'm trying to do a pwm amplifier in order to control 3 fans with one pwm signal. Since there are three fans and according to the pwm specs allowed current per each is 5-8mA, I expect current load of ...
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What is the purpose of these extra 'level shifter' BJTs on a MOSFET H-Bridge?

I am working on a 2WD Arduino project. Making the H-Bridge myself, and not using an IC like the L293 is a requirement for my project. After searching a while, I came across this, and based on this I ...