Questions tagged [class-ab]

This tag can be used to denote questions related to analogue amplifiers working in AB-mode.

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5
votes
2answers
174 views

How to bias a MOSFET class AB amp?

I'm working on a class AB amplifier that is used to either source or sink current. The reason for using MOSFETs is space constaints and that high power BJTs are only available in large leaded packages....
3
votes
3answers
283 views

What do these components of an AB amplifier do?

I'm trying to learn about class AB amplifiers by reverse-engineering a few I see here on SE. I borrowed this schematic from this question as a starting place. Ignoring the fact that the circuit lacks ...
3
votes
1answer
88 views

How is the quiescent current and emmiter resistor determined on the driver and pre-drivers of a class-AB audio amplifier output stage

I am reading online about discrete audio amplifiers. I have learned about the input differential pair, the voltage amplifier stage, and now I'm learning about the output stage. I have learned that you ...
2
votes
4answers
2k views

Design a class AB audio amplifier

I am required to design a class AB audio amplifier to deliver 10W to an 8Ω speaker as shown, but I don't know where to start. The bandwidth is to cover the range from 20Hz to 18kHz. Input voltage is ...
2
votes
3answers
238 views

Why only common collector method is used in class AB amplifiers?

I have recently started to study about class AB amplifiers online, as a newbie, i have found every schematic of the class AB amplifier is in common collector circuit just like this Schematic i find ...
1
vote
3answers
114 views

Amplifier power problems, power supply limitations, or end stage base current draw

So I am experimenting with various signal generating, op-amp and power amplifier circuits. And I have limited access to technology. Where I am at, everything you buy is twice the price because of ...
1
vote
1answer
123 views

How do analyze input impedance of Class AB amplifier biased with resistors?

EDIT: I realize that the original circuit is deeply flawed and will burn up upon re-entry. Thanks to anyone who can help me understand why! I'm learning to analyze Class AB amplifiers, but haven't ...
1
vote
1answer
43 views

What equation do I use for simple class AB input impedence?

I'm a novice at this. I've done some figuring and would love to know if I've got this correct before I move to more complicated circuits. I have the simplest Class AB amplifier and I'd like to know ...
1
vote
2answers
77 views

How can I calculate low and high frequency in my circuit?

How can I calculate low and high frequency in my circuit? I have used an 8-ohm speaker.
1
vote
1answer
428 views

LTSpice produces incorrect simulation for Class AB amplifier

I have been building a Class AB amplifier simulation using LTSpice. While it simulates well for transient analysis (voltage gain of 0.9 at peak), using ac analysis the the voltage gain drops to 0.268....
1
vote
2answers
108 views

Two-stages class AB amplifier

I'm studying the following two-stages class AB amplifier: Basically it is a standard two-stages op-amp (i.e. the cascade of a differential pair with active current mirror followed by an inverter with ...
1
vote
2answers
71 views

What is the role of the Op-Amp integrator in this circuit?

Helo dier community! I got a 400 Hz broken Power Inverter and reverse-engineered the circuit just for the simplicity of repairing it. Then I got deeper in and started to understand the engineering ...
1
vote
1answer
137 views

Cross coupled Class AB output stage

A simple question about ClassAB common source amplifier. There are two circuits which I have attached with this question, the one on the left is a standard cross coupled circuit which I have taken ...
0
votes
1answer
58 views

BJTs dangerously getting hotter as drawn current accumulating

I already ask a few questions on this project (so i won't explain everything again as it would be too long). I basically have a high power opamp (OPA462) to which i feed a signal (but i offset it ...
0
votes
1answer
318 views

Class AB Amplifier - Q point

In a class AB amplifier, why is the Q point much closer to the cutoff voltage as compared to a Class A amplifier which is at the center. Wouldn't this clip the AC signal if its too close to Vce. ...
0
votes
1answer
60 views

How should I size the transistors in the class AB linear amplifier

If I want to design a class AB linear amplifier as the following one, how should I determine the width of the pmos and nmos? Class AB amplifier specifications: Vdd: 6V Input: 0.5V to 5.5V Output ...
0
votes
1answer
117 views

Class AB Amplifier - Weird oscilloscope output

I have built this little kit for a class AB Amplifier. This is the schematic if you do not want to follow the link It works fine, I can hear decent sound. I then tried to check the output with an ...
0
votes
1answer
61 views

Adjustable power supply from +5V to -5V

Depending on the orientation of a nulling coil I need an adjustable voltage supply from ~+5V to -5V upto ~200mA. I've tried a few circuits similar to Class AB amplifiers such as the one shown below, ...
0
votes
1answer
86 views

Complementary pair - Role of capacitor on emitter

I bought this little kit for a class AB amplifier. The second stage is quite clear (and typical), but I am struggling to understand the role of capacitor C2 on the emitter branch in the first stage. ...
0
votes
0answers
62 views

Class AB linear amplifier design

I am trying to design a class AB linear amplifier. The required peak current is 450mA. I am just using an ideal biasing at this stage. The schematic is as follows: Here are the resulting waveforms. ...
0
votes
0answers
48 views

Class AB amplifier using push-pull pair signal decay

I'm trying to build a class AB amplifier with push-pull pair of power transistors for audio amplifier. the circuit works fine with low voltage(~0.2V) but the input peak voltage varies between 0.2 - 2V....
0
votes
1answer
76 views

Calculating output impedance without measuring open-loop output voltage of a push-pull Class AB MOSFET Amplifier

So I am building and analyzing a Class AB / push-pull amplifier implemented with MOSFET as depicted in the following schematic: R2 is the load. The input is an AC signal with 3V amplitude and 1KHz ...
0
votes
3answers
114 views

How can I overcome the distortion using in this circuit by using same products as we see in picture ? Or we can use 2n700 series, 3906 and 3904 bjts

Or we can use 2n700 series, 3906 and 3904 bjts. My aim is 10W, gain 100-1000 (adjustable), 50hz-20khz amplifier by using this basic components.
-1
votes
1answer
108 views

Class AB Amplifier With Single Supply [closed]

I'm designing an amplifier which is to be run off of a single 20 V supply (in the circuit, V+ = 20 V, V- = GND). Q2 and Q3 are used to bias Q4 and Q1. Since the circuit is running off a single 20 V ...