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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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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43 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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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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121 views

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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299 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 ...
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127 views

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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352 views

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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863 views

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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1k views

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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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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252 views

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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323 views

Transfer function and frequency of Common-drain Colpitts with ballast coil

Whilst looking for a circuit to test some unidentified RF filters and coils I have lying about, I came across a FET based Common-drain Colpitts used in this youtube channel hosted by RF enthusiast ...
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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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2k views

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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814 views

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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318 views

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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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 ...