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Questions tagged [emitter]

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0answers
84 views

Why is a voltage across emitter and base required in a bipolar transistor?

I read the reply to this question but I cannot really make sense of it: In an NPN transistor, why doesn't current flow without applying a base voltage? if I have a npn-transistor and and apply a ...
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0answers
97 views

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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0answers
90 views

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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3answers
92 views

Infrared High Intensity LED with two anodes?

I got an infrared led emitter, with model ""L1I0-0850060000000" and the datasheet is plenty of technical data but I can`t find why it has three terminals - 2 anodes and 1 catode. Usually it's used for ...
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0answers
45 views

Drive 433Mhz emitter and Attiny with two coin cells

I would like to detect when the postman put mail in my box, so I was thinking about a simple attiny with tilt sensor (which would wake up the attiny) and a 433 MHz emitter: The problem is that one ...
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1answer
62 views

40 kHz Emitter Frequency Response

I've recently purchased 40 kHz transceivers and I tested its frequency response in anechoic chamber using a B&K microphone located 90cm away from the emitter. The response provided in the ...
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2answers
86 views

Does Differential Amplifier Emitter behave as ground in AC-analysis?

I am trying to solve various differential-amplifier homework problems for which I have the solution to study. For the simplicity of most problems we are able to neglect base-currents. Moreover, it ...
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3answers
260 views

Are IR emitter frequencies adjustable? Can modulation of the emitter variate material absorption properties?

A common LED emitter, Gallium Arsenide, apparently has a wavelength of about 760 nm. Then on the receiving end, there is a filtering circuit to eliminate ambient IR and to demodulate the message. Can ...
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2answers
1k views
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3answers
199 views

AC Analysis of emitter circuit, why can I ignore resistance R1 but not Rc?

I am trying to calculate the small signal voltage gain of this circuit but I am having a problem comprehending the last step. I rewrote the circuit like this But the solution says this: Which would ...
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1answer
1k views

How to calculate the collector resistor of this emitter circuit?

My supply voltage is +10 V, collector current at my bias point is 5 mA, base current is 28.8 uA, amplification is 173.3 I already calculated the base resistor to \$R_1=\frac{V_{CC}-V_{BE}}{I_b}\$ and ...
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2answers
238 views

Collector must be more positive than the emitter

My book (The Art of Electronics by Paul Horowitz and Winfield Hill) is stating something that seems to be the opposite of the example it is using. I am not going to school for my studies so I ...
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1answer
914 views

Are there any SOT-23 BJT's with swapped Base and Emitter pins? [closed]

The standard NPN BJT in SOT-23 package has the following arrangement of pins: Do you know of any transistor that has pins 1 and 2 reversed? So that 2 is the base while 1 is the emitter (Doesn't ...
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5answers
3k views

Finding the Base-Emitter Voltage in an NPN Transistor

The problem asks to find the the real value of base-emitter voltage, \$V_{BE}\$ and the corresponding \$I_C\$, and \$V_{OUT}\$ in the figure below: \$V_{CE(sat)}\$ is given but the transistor is not ...
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1answer
67 views

Are there methods to stabilizing \$V_{BE}\$ [closed]

For \$V_{IN}\$ >> \$V_{BE}\$ (\$V_{IN}\$ in reference to GND), the \$V_{BE}\$ is quite stable typically only varying in 8mV for silicon NPNs and gets smaller when the emitter is conducting less ...
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4answers
321 views

Finding the Real \$V_{BE}\$

In a BJT in common emitter configuration, what formula can you use to calculate the real \$V_{BE}\$ so that you don't have to approximate it as \$0.7V\$? The problem below asks for the actual value of ...
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1answer
188 views

NPN transistor energy drain from base to emitter?

I have the following example circuit: I do not understand why this lights the LED. For my main project I am building a circuit that has a button connected to an output as well as the collector of the ...
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1answer
2k views

What are the reasons that the emitter is heavily doped in an NPN BJT? [duplicate]

Is doping the emitter more than the collector crucial? Would current not flow at all if both regions were equally doped? Why? Is there a way to explain this in a simple fashion?
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3answers
238 views

Why are these resistors considered in parallel in the DC equivalent (Com Emitter Amp)

So here is a page from my text book, the Common Emitter Circuit is on the top and on the bottom right you can see the DC equivalent circuit , my question is that by looking at that dc circuit i do not ...
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3answers
567 views

Finding the operating point of a transistor circuit

I want to find the operating point of this circuit: where we have a npn-Transistor and \$R_V = 47k\Omega\$, \$R_C = 1k\Omega\$, \$R_E = 4,7k\Omega\$, \$\beta = 100 \$, \$+U_B = 10V\$ and \$-U_B = -...
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1answer
295 views

IR emitter LED with jack 3.5

Currently I'm using an IR LED connected directly to a PCB where an Arduino UNO is connected. When I send a command with the Arduino, the LED sends what I want to an IR receiver. Now I'm thinking to ...
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1answer
78 views

Calculate the parallel value of resistors at base of common emitter amplifier

I don't know if questions can be asked like this here but if they can I want this question. In an exam paper I saw a question to determine the parallel value of the R1 and R2 resistors in the image ...
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1answer
174 views

Pspice Common Emitter Schematic Missing Values

I am doing some homework for universiy and PSpice keeps saying that there is some missing values.I cant seem to find a solution in my books so I though that i might share my issue with you and ...
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4answers
2k views

A question on voltage divider resistances used in BJT biasing

I'm reading a text on BJT common collector amplifier biasing. Text says: The voltage divider (R1 and R2) is used to give the input signal (after passing through the capacitor) a positive dc level ...
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3answers
1k views

Confusion on the meaning of a BJT emitter follower's output impedance

Above figure is a BJT transistor emitter follower. I can understand that in an emitter follower when talking about its input impedance what meant is Vb/Ib and here it is equal to (hfe+1)*R. The idea ...