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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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 ...
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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 ...
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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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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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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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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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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. ...
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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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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 ...
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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 ...
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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\$)?
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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 ...
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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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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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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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All possible BJT circuits relating to polarity

The BJT can operate in 4 different modes/zones since there are two voltages on it: Active mode Inverse/Reverse active mode Saturation mode Cut-off mode Because Emitter and Collector junctions can ...
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Common Collector Biasing

The common terminal of the transistor configuration is also the GND of the circuit, right? I get it that emitter is GND but how is it possible for NPN transistor that base or collector is GND?
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Misunderstanding of amplifiying a current with transistor

Electrical books say that we can use transistor to amplifying current but when I simulate a circuit in proteus input current, it is smaller than emitter current but why? This is a common collector ...
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CC-CE multistage amplifier

I've an unsolved exercise to ask. The circuit is shown below: The first question ask to find a value of R2 for which Vout = 0 with Vin = 0. I think this question is referred to the small signal ...
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Common collector amplifier current amplification [duplicate]

given: Re = 500 Ω Rb = 261 kΩ What can we tell about the current amplification? Is this circuit useful?
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BJT Common Collector not swinging "negative"

I have an R2R DAC generating a 0-3.3V sine wave. This sine wave is fed into a non inverting op amp with a gain of 2. Then I'm trying to drive a 0.5W 50ohm speaker with a common collector amplifier. ...
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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 or ...
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Cascading Common-Emitter Common-Collector for maximum power transfer

Hi Am trying to understand what am doing wrong, I connected CE to CC with a small Rload am designing it so Zout of the second stage equal Rload to get Maximum output. From what i read in CC-amp Zout =...
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How does this power supply circuit work?

This is the circuit of a power supply with adjustable output voltage and current, and I wish to understand how it works: What I did understand: R1 T1 VD5 - they form a voltage divider which provides ...
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