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Questions tagged [common-emitter]

A common emitter is one of three basic bipolar junction transistor (BJT) amplifier topologies. It is notorious for a high power gain. It is the only one-stage BJT amplifier topology that permits gain both in voltage and current.

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Common emitter amplifier gain with load resistor?

I have a problem I am working on where I have to find the voltage gain of the following circuit with a dc collector current of 0.3mA. My attempt at a solution involved using the formula A=-(RcIc)/Vt ...
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70 views

Calculating grounded emitter amplifer distortion (Art of Electronics 3rd Ed.)

Referring to section 2.3.4 A1 (pages 94-95) of the Art of Electronics 3rd Ed., I'm having difficulty understanding how to calculate distortion of a grounded emitter amplifier. The book says: ...
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35 views

What happens to the low cut off frequency when replaced with a larger bypass capacitor?

When the emitter capacitance is increased to 100 microfarads. What would happen to the low frequency cut off of this amplifier?
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What is the ouput of this common emitter amplifier? [closed]

I need to know the output of this common emmitter amplifier circuit. I was wondering if anyone knows what the output of this circuit drawing would be I ran this through the Falstad simulator and it's ...
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For MMBT2222; How to get hfe value to calcluate minimum base current to drive transistor in Saturation?

If my collector current VCC = 3.3V & Ic = 31.82uA then how to calculate minimum base current is required put transistor in saturation mode? Depending on it I will calculate base series resistor ...
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36 views

Charasteristic curves for a transistor working in a common emitter configuration

Configuration According to my text book, When we use a transistor as an amplifier, there generally 2 resistors, one is input resister(R in) and the other is output resister(R out). Normally ...
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72 views

Voltage gain of common emitter amplifiers with negative feedback

Im trying to make some fuzz pedals for guitar using a single transistor. The one on the right is as far as i understand a common emitter amplifier with negative feedback, I somehow can't find anything ...
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92 views

How can I set the quiescent current for a grounded-emitter amplifier?

I'm currently learning about common-emitter amplifiers in AoE3. I learned how to set the quiescent current for an emitter-degenerated amplifier. I simply choose \$V_E\$ and \$R_E\$ such that \$I_E = ...
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52 views

Voltage gain of common emitter amplifier

I'm posting this question just to be sure I'm understanding this correctly. I want to estimate the voltage gain of the following common emitter amplifier either as \$A_v=-4.7\$ or \$A_v=-145\$. It'...
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110 views

Why collector current is small in value in saturation mode?

Why is the collector current smaller in value when a transistor is in saturation mode of operation? My guess is that although both the junctions are forward biased, the (forward) currents are '...
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52 views

Determining collector-emitter voltage versus collector current for a phototransistor

I'm using a Vishay TEPT4400 phototransistor (datasheet) and want to design a circuit that gives an output (Vce) of 1V at 200 lux and 5V at 0 lux. I'm using a simple common-emitter configuration , but ...
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306 views

How to derive the precise gain of an NPN common emitter amplifier without emitter degeneration?

As a self imposed exercise, I tried to derive the complete expression of gain in a common emitter amplifier without emitter degeneration. I mean by "complete" that it also takes into account the ...
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176 views

Common emitter circuit - can't understand negative feedback

I have a problem with understanding how does the negative feedback of this circuit work. In all books that I read it is said that "with the rise of temperature, collector current increases". Why is ...
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1answer
110 views

What causes amplitude clipping of single stage CE BJT amplifier with a bypass capacitor?

Where is a single stage CE BJT amplifier with a bypass capacitor supposed to clip with a normal 4-resistor biasing circuit? Like I seem to be able to get the upper peak of the output voltage all the ...
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102 views

What is the impedance of this Common Emitter transistor

I see this question on EE but the other question is slightly different of what I am asking. Suppose this circuit: Suppose I will add a capacitor to the input but I need to calculate the input ...
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100 views

Why can't my BJT common emitter trigger the pin interrupt of an MCU?

I'm trying to build a noise detector that gets triggered by pretty much all audible noises, provided that they are loud enough. The schematic design is as follows: simulate this circuit – ...
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54 views

Common emitter: maximize effective voltage gain

My homework is to design npn common emitter amplifier, with minimum output aplitude=5V, powered by +26V and -20V with generator resistance=40kOhm and output resistance=10kOhm. I have calculated ...
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268 views

Calculate Thevenin voltage in a Common Emitter Circuit

I am confused on how to proceed with the above problem. I have solved many problems on thevenin voltage but never faced one involving BJT. Please help me with this problem. EDIT: I have 2 approaches ...
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Split supply common-emitter [duplicate]

Please assist me with this design problem Design and construct a single stage common-emitter amplifier with the following characteristics:  The voltage gain should be at least 100V/V;  The input ...
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360 views

What is a common-emitter bjt push-pull output stage?

My professor mentioned it briefly in class, and I've been googling it and all I find is the CC output stage. Can anyone show me a picture of this configuration and maybe describe how it works? Can you ...
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94 views

Common Emitter, can't understand how collector current is found

So there is this common emitter transistor and it says Ic = (Vcc-Vce)/ RL, what I'm not understanding is why Ve is totally ignored, I thought Ic = (Vcc-Vc)/RL. How come the Emitter resistor is totally ...
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112 views

Identifying the configuration of transisitors

I have been handed the diagram below, as part of an introduction to transistors. I am having a hard time finding out what type of configuration it is, therefore making it even harder for me to find ...
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153 views

Why BJT BE voltage allows to avoid distortions

In Common-Emitter amplifier the BE voltage is set near 0.7V but we apply both positive and negative swings to BJT and there is no distortion on output but the signal will be 0.7V+signal_value and 0.7V-...
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474 views

Common Emitter Amplifier Voltage Gain

I'm trying to design a common-emitter amplifier with a gain of 25. I seem to have gotten the correct gain by guessing with my resistor values. Can anyone tell me how to calculate resistor values and ...
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85 views

CE transistor curves

I've created the following simulation on LTSpice and I'm running a DC sweep for V1, I1: .dc V1 0 5 5m I1 0 100u 10u. After the simulation is finished, I get those two graphs for \$ V_c=f(V_b)\$ and \$...
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Can anyone make sense of my electronics instructor's common emitter design?

I think that I need to give a little back story, but I will try to make it short enough as possible. I have a 2 year degree that I describe as half hardware/ half software. What I mean by that is half ...
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406 views

Dual Feedback Transistor Biasing a Common Emitter Amplifier

I was reviewing/following a tutorial describing the pros/cons of various transistor base biasing configurations. Configuration #4 is shown above. Resistor Rb2 was added to what was previously ...
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163 views

Common-Emitter Behavior

I built circuit shown bellow (NPN BJT): simulate this circuit – Schematic created using CircuitLab Everything worked normal as it should (except of unwanted distortion). There is that one ...
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228 views

common emitter amplifier output distortion

why the output of the Amplifier is distorted? the input from the function generator is 1 Vp the amplifier is baised at collector voltage of 4.5 V the frequency of the input signal is 1 khz the ...
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533 views

current mirror as active load in common emitter amplifier

Could someone help to analyse the circuit above, which is a single common emitter amplifier. And for the purpose of larger voltage gain, a current mirror building block is applied as active load. But ...
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111 views

CE amplifier circuit gives output voltage that is not completely out of phase

This is the circuit that I have constructed But it fails to give the output voltage that is completely inverted (out of phase) Can anyone show me whats wrong with the circuit?
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219 views

BJT Emitter Degeneration Rπ

I am a bit confused about this differential base-emitter resistance. I has been said that r_pi doesn't have much influence on small signal input impedance, when CE with emitter degeneration is used. ...
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288 views

Collector current for common-emitter audio amplifier

Looking at building an audio amplifier; many good example circuits and example tutorials based on the below simple common emitter circuit. All of them I have found so far help to size the biasing ...
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381 views

Importance of Common-Emitter Input & Output h-parameters

Speaking for NPN Bipolar transistor: In many practical examples parallel resistance of base-emitter junction (aka hie) and finite collector-emitter parallel resistance resistance (aka hoe) are ...
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194 views

Two-Stage Common Emitter Amplifier Is Clipping Unexpectedly

I've been reading about multistage common emitter/source amplifiers and have decided to test some high-gain designs with PSPICE. One design has me very confused and I was wondering if someone could ...
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557 views

Why are there two diodes in series in this test circuit?

Look at Figure 2 in the following datasheet: http://www.onsemi.com/pub/Collateral/MMBT3904LT1-D.PDF Why are there two diodes and not just one? Thanks.
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688 views

Understanding common terminal in common collector/emitter amplifier

I am beginner in electronics and trying to understand some basics. One thing that confuses me is transistor configuration with common terminals. Since transistor has three terminals then we must use ...
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490 views

Why are they connecting the input signal parallel to the dc source?

My textbook says the voltage across \$BE\$ would be \$0.7+v_i\$. But this looks incorrect to me based on the shown circuit. It seems the \$v_i\$, \$V_{BB}\$, and the base diode are in parallel. We are ...
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117 views

How can emitter bias amplify since the emitter current is fixed?

My textbook says \$I_E\$ is fixed at \$V_{BB}/R_E\$ no matter what the current gain of the transistor is. This is confusing me a lot. Since the emitter current cannot change, how can this ciruit ...
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98 views

Transistors - The change in the base current

I came across this question in my book, it says: what will happen to the output voltage if we increase the base current in the figure below? What confused me in the figure is that the output ...
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1answer
381 views

Calculation of common emitter output impedance with output resistance

[ I don't understand why \$g_{m}\$ survives. Since \$v_{\pi}\$ is equivalent to \$\Delta V\$ , which is perturbation of signal, which is then set as AC ground. Doesn't that mean \$v_{\pi}= \Delta V = ...
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278 views

Common emitter with low voltage input

I have to do a project involving a common emitter amplifier. The only given data is: the amplitude of the input signal is 100u, and offset voltage is 0. I need that signal to be amplified. But my ...
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1k views

Active region in BJT in a Common emitter configuration

In BJT for working in active region for a common emitter configuration emitter and base should be in forward bias and base and collector should be in reverse bias. But in case of voltage we say that ...
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311 views

Common emitter voltage amplifier does not work

Since I'm a beginner to electronics, I'm trying to build the following circuit in order to see the way a common emitter amplifier works. I'm using the transistor of type BC547, as indicated in the ...
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284 views

Collector voltage in saturation

I saw the following question online I knew that while Vbe was less than 0.6v, there would be no current and the collector voltage would be Vcc. At 0.6V, I knew that the transistor would turn on, and ...
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569 views

How do you calculate the voltage output of a common emitter amplifier

How would you calculate Vout given Rc, Vce and Re? I used the voltage divider and got a strange answer. I'm asking this because there was a question on my advancement exam that made me think of this ...
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124 views

Why base current changes with collector emitter voltage?

There are two questions in stack exchange similar to mine, but I though mine was more basic and also more specific. I tried doing some SPICE simulations in order to understand transistor ...
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188 views

\$V_{BE}\$ decreasing with \$V_{CE}\$ at constant \$I_B\$ in a BJT common emitter?

I took measurements on a TIP31 common emitter BJT transistor. The circuit was the one in picture I observed a fact which seems quite unusual. Keeping \$I_B\$ constant, for different values of \$V_{...
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1k views

Solving for the Voltage Gain in Cascaded Two-Stage Amplifier

First, I drew the cascaded small signal equivalent circuit (unilateral hybrid pi transformation) for Figure 3 as: After drawing the cascaded small signal equivalent circuit (unilateral hybrid pi ...
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497 views

Solving Currents in BiCMOS Darlington Pair

Using KVL and assuming that the BJT is in forward-active and that the MOSFET is under saturation and using the given, I was able to generate three equations with three unknowns: 1) \$\frac{3V-2V}{...