Class A Class B or Class AB - How to set the bias current with Micro-Cap Tutorial #microcaptutorial

This is discussion about what makes an Amplifier Class A or Class B or Class AB? I will talk about the bias current that changes the Class of operation. I'll then show a simulation to illustarate how the bias looks under operation. Micro-Cap will be used and the 20W Class A amplifier schematic will be used in the simulation. It is titled Class A Class B or Class AB - How to set the bias current with MicroCap Tutorial. #microcap #microcaptutorial #micro-cap #classaamplifier #classABamplifier

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Yaung Jing is the brand, and the following is the specifications for it:
Basic Parameters
Supply voltage: DC +/-25V ~ +/-35V
Output power: 20W @ 8 Ohm, 40W @ 4 Ohm, 80W @ 2 Ohm
Speaker impedance: ohm 2 ~ 8 Ohm

Please use this link for the Hiraga Power supply kit:

Another Aleph 5 Class A amplifier link:

[AllboroLCD]

This was fantastic, I million thank yous! I understand the functionality of the classes better, im not fully grasping exactly how I need to apply this to my current amp project yet. Some things take me some time to fully absorb! Great stuff here either way!!

[MichaelBeeny]

Looking at everything, heat, distortion, class AB is the answer, with a little on the warm side for the bias. Class B was used a lot in old 60/80s portable radio's were battery life was more important than fidelity. Probably where the early, so called transistor sound came from.

[Patrik_]

Really nice overview. Gives me courage to start simulating myself.

[TRONMAGNUM]

Thanks for the explanation. Learned a lot.

[wafiullah-shafia]

Thank you
Good that going inside amplifiers

[frankgeeraerts]

Thanks, nice explanation ....I am still asthonished by this subject be'cause it is so missunderstood by many audio fans fact class AB is an aberration as it is only a switching from class A into class B every bias current mode between A and commuting to so called class A amplifiers are in reality hot biased class AB most class B amps have a slall amount of bias current ..
Tubes don't suffer as much of temperature issues as transistors
I like class A amplifiers, as I must admit some good class AB come close

[ianhaylock]

Hi, nice explanation. I was just wondering, if the positive transistors are running much hotter than the negative transistors, would it be possible to design the circuit so that you have separate bias's for the negative and positive transistors.

[jesusrojas]

Hi, there. I have a behringer gmx212 v-tone modeling amp class b. I was wondering if it's possible to modify it to make it a class ab amp and how it can physically be done, and if so, can you show us how to do it? Thanks

[abhilashgerman]

Thanks 🙏, Sir, Can you suggest a good sub filter hz/120

[scottbrady]

Thanks for the lesson Eddie. I built on a simple Class A and a simple Class AB amp on Micro-Cap, but I can not get a decent amount of voltage at RL. The biasing seems correct to me. I've tried driving the voltage higher, changing resistor values and transistors. Also, I don't know what all the transistor info is telling me. Do you have a video explaining the data sheet acronyms from Micro-Cap? Even when I find a design on the internet and build it out in Micro-cap, it doesn't seem to work for me. Can I send your both of these files for your review?

[betheout]

i have a diy (not made by me) Krell ksa-50, it is 50watts classA. could i tranform it into a class A/AB mix so i have like 100watts on 8 ohm? just by changing the value of the 'bias-resistors' ?

[thomassorensen]

Hello. How is the feedback with the Opamps determined?

[Taylor_GE]

Does the bias currents have any impact on the output noise levels? In terms of white noise etc. Not distortion.

[markbosold]

Nice video on amplifier biasing and operational classes. I'm learning a lot and filling in my knowledge gaps while watching your videos. Thank you for doing what you're doing! I'm new to circuit simulation, is it possible to look at frequency domain to estimate THD with different bias points?

[joshaas]

oke first of al a real good video, thx for that easy to understand explanation, it's simple this way to understand, you are a good teacher, now for the amp, i like to see the distortion u get from setting the amp in lets say a hot A/B, so let's say the first 10 watt are in class A and the next say from 10 watt to 20 watt its A/B, what's the distortion on that amp bias like that, i think its 0, 6 amp until 0, 8 amp bias, and what's the distortion if u go the hole way to class A, so the bias at 1, 2 amps, with my Hood 1969 amp the bias need to be 1, 3 amps to get the hole 20 watts in class A, and maybe not only simulate it but do it to the real amp so that u can see if the simulation is correct or not, is the real amp close to the simulation, that's what i like to see, so again very good video thx for that

[Nightjar]

In my Marantz HD DAC1 there is a headphone amp. And they recommend biasing to 50mV.
How do I know how high I can go?
It was 95mV when I got the unit but I bought it used. Maybe someone biased it hotter.
But how do I know where to set it so I don’t get crossover distortion?
Thanks

[berth]

Good video but in your schematic the LED is shorted..

[davidkclayton]

Couldn't you use the resistor diode combination for thermal protection for Q10?

[jeffersonavila]

what software did you use as simulator? tnx

[JensenTech]

I have a question. If it's biased with 2 amp, how many watts will be in class a in 8 ohm? Can you show the math? Thank you.