Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [emitter-follower]

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

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

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What does this transistor circuit do?

I found a schematic which had this bit of circuitry between the +9 V (which apparently the author assumed to be > 9 V, more like 10-11 V) barrel connector and the +9 V supply rail. I tried to simulate what's happening in LTspice, but I don't think I…
Xaser
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What is the basic idea behind the so-called "diamond buffer"?

The idea for this question came about after I wrote an answer to a similar question. This "diamond solution" was something unknown to me. I took a look at Wikipedia page (see the picture below) and it immediately impressed me. (The picture is taken…
Circuit fantasist
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Art of Electronics: Emitter-Follower Zout

I am a growing frustrated with the Art of Electronics. It is such an approachable book in Chapter 1, and then in Chapter 2 it seems like the authors wanted to make it more textbook-like and they start dropping information in lieu of exercises. I…
Dr. Watson
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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 simulate the circuit: Just after checking the…
Fuad Zadeh
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Opto-isolator output from collector vs. emitter

I have an Isocom ISQ2X quad opto-isolator (datasheet) that I will use to drive a logic input. The opto-isolator's simplified model given by the datasheet is pictured below. The transistor base pin is not brought out. I have two possible…
GummiV
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Emitter follower

I'm having a hard time understanding an emitter follower. What I don't understand is why there is no voltage gain but only current gain. From my understanding when the transistor is turned on, the CE acts like a piece of wire, so the Vout should be…
user225045
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Down-converting voltage

I'm trying to reduce the voltage of a power supply for a certain load without affecting the current the load draws. Since the op-amps I could find were not able to provide sufficient current, I added a NPN transistor to the output of the op amp as…
user172226
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Emitter follower regulator with sziklai pair, transistor heating up!

I have a wireless chip esp8266 that requires input voltage of 3.3V and can draw current up to 500mA. Unfontunately at the moment I don't have any 3.3v regulator IC's or buck converters or any 3.3v voltage source, so as a temporary measure (until my…
razzak
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Why the base current decreases automatically?

Given this circuit: simulate this circuit – Schematic created using CircuitLab I don't understand why, when simulating it by increasing parametrially the V2 from 0V to 12V keeping V1 constant, the base current decreases exponentially until V2…
thexeno
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How to select resistor for emitter follower when driving speaker?

simulate this circuit – Schematic created using CircuitLab The objective is to drive 1 watt into the speaker. R1 represents the output impedance of the previous common collector stage. Here's what I think I know: 1 watt into 4 ohms means 2V RMS or…
Willis Blackburn
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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 a voltage referrence that is applied through a…
Denis Denisovici
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Emitter Follower Output

I cannot afford a function generator and oscope right now, so I'm trying to learn analog electronics with Spice (MacSpice, to be specific). Below is the Spice model for a simple emitter-follower circuit. Vcc is 15V, and the input at the base is a…
Dr. Watson
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Emitter follower: Icq and Vceq calculation

I have problem with understanding how to calculate \$ I_{cq} \$ and \$ V_{ceq} \$ of this circuit. Q1 has these details: \$ h_{FC}=150 \$ and \$ h_{fc}=100 \$ As I understand it I should find \$ V_{B}=V_{cc}(\frac{R_2}{R_1+R_2})= 6V\$ then…
Faux_Clef
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Operating region for transistor in capacitance multiplier

I want to understand what is the desired operating region for a transistor in a capacitance multiplier circuit being used to remove power supply ripple. Consider the circuit in the attached image. From what I understand, depending on R1 and R2, for…
Diggs
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The need for a current source in an emitter follower

What is the need for adding a current source (\$I_\text{E}\$) at the output of an emitter follower topology at the emitter leg of the transistor?
G.Hajj
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