Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [class-a]

For questions about class A amplifiers, in which the active element conducts all of the time. Other amplifier classes include B, AB, and C-H. Compared to other amplifier classes, class A amplifiers are the simplest and have no crossover distortion, but are the least efficient. Consider using this tag in conjunction with the "transistors" tag.

For questions about class A amplifiers, in which the active element conducts all of the time. Other amplifier classes include B, AB, and C-H. Compared to other amplifier classes, class A amplifiers are the simplest and have no crossover distortion, but are the least efficient. Consider using this tag in conjunction with .

See Wikipedia's article on power amplifier classes for more information.

35 questions
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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 follower) amplifier to amplify power and deal with…
Rojj
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How to keep current from draining out the bottom of this push-pull amplifier?

In an earlier question I asked about driving a speaker with a BJT transistor. @Jonk offered a push-pull amplifier design of his own, and @G36 noted its similarity to the JLH amplifier described in a paper from 1969. In 1969 NPN power transistors…
Willis Blackburn
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4 answers

BJT base connected to ground and still operates?

When in university I used to get confused how a transistor (NPN) can draw current from ground. I'm now studying power amplifiers and again, this same configuration appears. How does Ir draw current from seemingly nothing/ground?
user160063
5
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3 answers

Low power tube headphone amplifier design

I have never worked or even listened to tubes/valves before, so its about time I did. I wanted a simple design to work with being my first tube project, and have found this from diyaudioprojects.com: After reading some forum posts about this amp,…
G Frank
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Presence of Crossover Distortion in Class A Amplifier

This question is about theory facts of class A audio amplifier. It is known that class A amplifier is usually biased so that an amplifier's quiescent point is in the middle of the amplifying device's load line. For class B amplifier is known that it…
Keno
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Transistor bias goes negative under input

I am trying to make a simple class A audio amplifier with one transistor (TIP41, NPN) in common emitter configuration as shown in the pictures. The problem I have is that when I add the input signal (more than 1 V), the transistor's base bias…
Alin Paladin
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Class A Amplifier Design: Emitter Resistance Voltage Drop

I am trying to understand the design principles of Class A amplifiers, primarily for audio purposes. I have read several times that "the voltage drop across the emitter resistor should be in the region of 1 to 2 volts"... To me this seems like a…
user3728501
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Why can't class A amp drive 8 ohm speaker with just one BJT?

I designed this class A amplifier. It's my first attempt at designing an amplifier with transistors. My objective is to build a guitar amplifier with tubes, but I figured that building an amp with BJTs and a low-voltage power supply first will…
Willis Blackburn
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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 source. I have read it is the right thing to do, but I…
Rojj
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Emitter-Follower Class A amplifier

I was trying to solve a problem from SEDRA-SMITH book. I got stuck so I refer to the solution. When Studying how the author solved the problem I got even more confused. Let's refer first to the given vbe and ic in the question. As per the…
Paumdrdo
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Class A amplifier - Transistor Q-Point calculation

Reference: http://www.learningaboutelectronics.com/Articles/How-to-find-the-q-point-of-a-transistor-circuit I am trying to understand this q-point calculation. I recently asked a question about the notation used, however I now understand…
user3728501
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Class A Audio Amplifier

I am trying to design a Class A Audio Amplifier with the following specs: 9V DC Power Supply, Maximum withdrawn current 15mA Used with a Low Impedance (8 Ohm) Speaker Provide a minimum variable gain of 10 Can work with frequencies from 20 Hz - 5…
Amr Mohamed
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What went wrong with this class A amplifier design?

I was trying to build a normal class A amplifier; However, no matter how hard I try, I cannot find the reason behind my output (BLUE LINE) being clipped at the negative cycle of the input (YELLOW LINE). What am I doing wrong? Any help is appreciated…
Yeal Takian
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6 answers

No voltage gain in a common-emitter class A amplifier using a 3904 NPN transistor - Ngspice simulation

I am currently trying to build an amplifier for a condenser microphone in order to use it as a way to amplify an acoustic guitar. I am having some trouble to achieve my goals. In order to learn I decided to make some analog simulations using…
Man789
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Discrete headphone amplifier output stage

What is the role of R13? I tried simulating this circuit using the Falstad simulator and removing it changed nothing. It is a circuit from Small Signal Audio Design by Douglas Self, second edition.
mrazoun
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