Questions tagged [common-collector]

A common collector amplifier (also known as an emitter follower) is one of three basic single-stage bipolar junction transistor (BJT) amplifier topologies, typically used as a voltage buffer.

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Why are only 3 of 6 single-transistor amplifier configurations useful?

Almost any analog design book or course I have ever seen starts by introducing the three basic single-transistor stages. For example, in a bipolar technology these are the common-emitter, common-base, ...
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How to design BJT common collector amplifier?

I am working on a school project and I am struggling to design what is supposed to be an easy CC-amplifier. All other parts of the circuit are calculated and should work. The power amplifier is what's ...
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Electrical characteristics on datasheet

What does this part of a datasheet mean? I always get confused when studying them... Is the user suppose to meet these conditions before getting the results stated on the sheet?
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Does my common-collector current amplifier work correctly?

I have just built a 9V common-collector current amplifier to make my RF receiver more sensitive for 1-8Mhz. I used a voltage source in this circuit to make it clear how the circuit might work. The ...
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6 answers
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How to tell what configuration a transistor has in a complicated circuit

Apparently transistor Q15 in the following circuit is in common collector mode (well, actually it says it's an emitter follower but my understanding is that this is the same thing as common collector ...
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Orcad: less than 2 connections on the emitter of the PN2222

I keep getting an error while simulating concerning the emitter node. Can anyone help?
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1 answer
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DC Analysis of Common Collector Circuit with current source at emitter

For the circuit below I have to derive IB, R1 and R2 Since it is a DC-analysis, I turn the AC-sources off and make the capacitors open circuits. So the circuit becomes the following IB is straight ...
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Should I use Thévenin to calculate emitter current for current in common-collector amplifier?

Determine the total input resistance of the emitter-follower in the figure below. Also find the voltage gain, current gain, and power gain in terms of power delivered to the load, RL. Assume \$\beta_{...
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Common-Collector amplifier as first stage to reduce input?

I am tasked with designing a multistage amplifier (maximum 3 stages) for a course project. The project asks us to amplify a sinusoidal signal with an amplitude of 20mV and a frequency of 20kHz. The ...
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1 answer
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Operating point for high current transistors

I'm a neophyte self-thaught learning electronics. I'm trying to amplify a DC current from a little less than 1 to 8 A using an NPN transistor. Currently I'm trying to figure out how even could I ...
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BiCMOS voltage follower analysis help

I am looking to mathematically characterize the circuit shown before, consisting of two (MOSFET) current mirrors and a BJT (common collector or emitter follower?). I am stuck at the first current ...
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Common-collector Colpitts oscillator with lossy inductor

I'm trying to build a common-collector Colpitts oscillator with a resonant frequency of 8 MHz. The inductor (20 μH) has a low q factor and can't be exchanged. The two capacitors should have 33 pF and ...
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Why is this a common collector transistor circuit?

This is a common collector transistor circuit: This is a common-emitter transistor circuit: Consider the following transistor circuit: This transistor circuit looks an awful lot like a common-...
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Common collector

I've created the following circuit in PSpice: I was asked to simulate the circuit and create its Bode plot. I have done that and ended up with this : I suspect that what I've got is incorrect ...
JustCurious's user avatar
1 vote
2 answers
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Node voltage increases in voltage divider

I am planning to use a voltage divider in order to measure the capacity of a group of lithium batteries; in order to minimize power consumption, I biased a common-emitter switch (Q1) with the ...
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Why would an emitter follower be DC-coupled to its input?

In my experience, an emitter-follower amplifier is usually AC-coupled to both its input and output: However, I recently came across such an amplifier which is DC-coupled - the capacitors C1 and C2 ...
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How does this DC offset sinwave input work?

I have learned that this circuit will move the sin wave up to a DC points due to the voltage divider, that is: V_out = V_in + Vcc*R2/(R1+R2) I was using LTSpice to simulate this and it works, I try to ...
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Saturation for emitter follower

How can a transistor connected in emitter follower configuration be driven into saturation? I know that for saturation, the base voltage should be greater than the emitter voltage, but also than ...
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Difference between CE, CB and CC transistor configurations

In the different configurations of transistors, namely Common Base (CB), Common Emitter (CE) and Common Collector (CC), I am asked about the basic difference. So can I say that the basic difference is ...
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What is the DC behavior of the switched BJT emitter follower configuration [closed]

There is a circuit shown below where we have a sub-circuit I marked in red. I know that it is a source follower with the AC behavior shown below. As you can see the circuit has DC voltage input only. ...
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\$R_e\$ when using a common collector amplifier

For the DC biasing of a common collector BJT amplifier, how to choose \$ R_e\$ to get a proper DC biasing? (see image attached). Furthermore, is it possible to control \$V_{ce}\$? I am confused. ...
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How to design a good common-collector amplifier?

I tried to simulate an example common collector amplifier given in the book Electronic Devices by Floyd. The circuit depicted in the book is: I used LTspice with transient analysis to implement and ...
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How do I increase the voltage gain of a Common Emitter + Common Collector without distortion in Vo?

I started with R1 and R2 half of what they were now, and with R_C = 5k. This had a gain of about 11, I managed to increase that by increasing R_C, but it seems to be plateauing when I start to get ...
Intradiction's user avatar
2 votes
1 answer
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Emitter Follower / Common Collector as Negative Feedback Amplifier

Background From the wikipedia page on Common Collector Amplifiers there is paragraph describing how the circuit acts as a negative feedback amplifier The circuit can be explained by viewing the ...
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Help solving thermal runaway in voltage follower circuit

I'm trying to build a circuit to drive a heating element. In testing a portion of the circuit, I've noticed what looks like some kind of thermal runaway in the Darlington transistor I'm using, but I'm ...
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2 votes
2 answers
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What "was" input resistance of this voltage-voltage topology amplifier before feedback?

I'm slowly working my way through understanding negative feedback in simple BJT amplifiers. I'm studying this circuit here: I read that one of the advantages to negative feedback in this topology is ...
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Why do I have clipping in this emitter follower

I am trying to design a class A amplifier buffer stage (I know it is not efficient.) I am starting from the simple emitter follower and the next step is to replace the RE resistor with a current ...
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Voltage-voltage Feedback and common-collector analysis?

(This question is related to this one here, where I attempted to understand how the discrete component values in a negative feedback amplifier are represented by the closed-loop gain and feedback ...
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Where voltage is lost in an emitter follower?

I'd wanted to know what happens in an NPN emitter follower with \${\delta}V=Vcc-Vee\$. At which junction does voltage drop? May this drop be fatal to a transistor?
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How to improve emitter-follower efficiency?

I’m trying to wrap my head around the emitter follower. I’m currently using it to simulate a ~12V AC coming from a intercom ringer (about 700Hz). simulate this circuit – Schematic created using ...
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Cascading common emitter and common collector

I am trying to design an amplifier for a 1 W 8 ohm speaker for educational purposes. The idea is to start from a common emitter amplifier to amplify voltage and then add a common collector (emitter ...
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In Emitter Follower BJT circuit Why the parallel resistance of the biasing resistors to be 1/10 of the Rin and not their series resistance?

Well In "Practical Electronics For Inventors" Book P.439 The Below Emitter follower circuit was introduced with the following explanation. The actual sizes of R2 and R1 should be such that ...
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2 answers
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pi model of common collector

I don't know to retrieve the \$r_\pi\$ value of common collector . re model (or pi model) for common emitter configuration Ok for \$r_\pi\$ model from common emitter with , and re model for common ...
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1 vote
1 answer
258 views

Collpitts oscillator signal distorted

I am trying to build a Collpitts oscillator using an 8MHz crystal, but the signal I get, is completely distorted. Any idea why? The yellow signal is probed at the output, while the pink is probing ...
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2N3904, Power Supply & FuncGen results on strange output on the scope

I was having trouble with a Collpitts oscillator output, it was distorted, so wanted to check if I am indeed in the linear region of the transistor, so I decided to use the func gen to check that. ...
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3 answers
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effects of hFE in emitter follower?

There are multiple hFE options for BD139s, with the higher hFE being slightly more expensive. What advantages or disadvantages, if any, would the higher hFE parts have in emitter follower circuit?
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Common collector :current amplifier or voltage follower?

I want to construct a simple voltage regulator like this one: simulate this circuit – Schematic created using CircuitLab However there is something peculiar: the voltage on the emitter is ...
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Derivation of output impedance of emitter follower or common collector amplifier (using Thevenin's Theorem ?)

I was going through the AC equivalent circuit of Common Collector Amplifier from ELECTRONIC PRINCIPLES BY MALVINO 3RD EDITION and I came across the analysis for the output impedance of the circuit. ...
Abhishek Ghosh's user avatar
1 vote
2 answers
207 views

Magnitude of \$I_{CBO}\$ in a typical transistor

I read in a book that \$I_{CBO}\$ doubles for every 10 degree rise in temperature and hence contributes to thermal runaway. However I am confused since essentially it is the reverse saturation current ...
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1 answer
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BJT common collector amplifier with a voltage gain sligthly higher than one

How could I explain why a common collector amplifier has a voltage gain higher than one ? In a lab session, I built this circuit : With Vg=30 mVpp and Vcc=15V, students were asked to give the voltage ...
Ethan B.'s user avatar
1 vote
1 answer
912 views

BJT (Common-Collector Configuration)

As we know that for the transistor to operate in the active mode, it should have emitter-base junction as forward bias and collector base junction as reverse bias. So the common-collector ...
John Cena's user avatar
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1 answer
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Capacitor in common collector circuit

I have a question regarding \$C_1\$ capacitor - do we really need it in this circuit if we know, that the input signal will have no offset (i.e. \$\overline{V_{IN}}=0V\$)?
SantaXL's user avatar
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2 votes
3 answers
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Common collector transistor

According to my understanding the common collector transistor should be like figure-1 but in book it is given as figure-2 and in it Vcc is given.Can anyone provide me proper explanation of this.
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A good and valid example of Common Collector BJT

I am analyzing a common collector BJT as an amplifier using LTSpice. I have made the following circuit and I am not getting the exact characteristics which I should have got. Is there something wrong ...
Himanshu Sharma's user avatar
2 votes
1 answer
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How to determine the input resistance of a bootstrapped emitter follower

I've used bootstrapping several times, either to boost the input impedance of an amplifier or to increase its gain. However most of the times I can see the beneficial effects of bootstrapping without ...
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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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2 votes
2 answers
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Emitter follower/Common collector confusion

I'm in the need of a buffering circuit for a project and I would like to use a common collector amplifier or emitter follower for this purpose. Above is a schematics of the circuit I'm looking into. ...
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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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How to calculate output resistance in a common collector circuit?

Calculate output resistance \$r_a\$. Here is the solution: $$ r_a=R_E || \left(\frac{1}{g_m}+r_a'\right) $$ $$ r_a'= \frac{U_e}{-i_c}=\frac{U_e}{-\beta i_B}=\frac{R_G || R_B || R_V}{\beta}$$ I don'...
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1 vote
2 answers
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Single supply op-amp voltage follower - negative clipping with AC-coupled load

I am using a µC running DDS algorithm to synthesize certain waveforms (in fact I made 3 channel music generator with portamento&ampltude modulation effects, commands for changing waveforms etc. ...
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