AB100 Class AB Power Amplifier

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#301
I also noticed that the bias difference between each the Darlington transistor (MJ11015 and MJ11016 from ON semi) ar minimal - in range of few mA.
Standard ON semi MJ 15003/004 bipolars which I use im my leach amps - their individual bias difference is much greater - even up to 15-20mA.
 
#303
AB100 amplifier was operated continuously 10h by me at moderate volume.I checked parameters now - bias stable compensated from 100mA per transistor to 90 mA. Offset - from 3mV dropped to 1.2mV and 12mV on other channel. (diff pair transistors was matched by hfe) .sounds very good - the low end also impressive.
 
#305
osscar said:
AB100 amplifier was operated continuously 10h by me at moderate volume.I checked parameters now - bias stable compensated from 100mA per transistor to 90 mA. Offset - from 3mV dropped to 1.2mV and 12mV on other channel. (diff pair transistors was matched by hfe) .sounds very good - the low end also impressive.
Click to expand...

How you match the darlingtos, do you use some circuit etc. With a simple DMM you can not do it.
Please let me know
Thank you
 
#306
Hello,
I matched only the input pair transistors not darlingtons, but they are already pretty close to each other from the store shelf - maybe I'm lucky. (Which I doubt ..)
I think its possible to reduce Re to some 0.33R instead of 0,5R .
 
#307
east electronics said:
In between enjoy the schematic ....This is a commercial design existing in the market for a number of years and also features a patch of 150Pf in the upper side Only ! relatively low next to known other schematic .
Click to expand...

Thanks - It's (vaguely) a Blameless clone with a cascoded VAS and Darlington OPs. They have gone through some pains to include an elaborate Vbe bias limiter to reduce the possibility of thermal runaway - perhaps the added cost of such a limiter was much lower than the price of discrete non-Darlington outputs + drivers in that era (maybe even today, even with inexpensive C5200/A1943 clones from the likes of ST).

The discrete darlington VAS of 2x BC560 is wasted. They should have used a true Blameless-style emitter follower, with collector going to ground. Perhaps you can do that mod, though the extra open-loop gain may tip it into instability.
 
#308
In the last few months ab100 has become my everyday amplifier - I like everything, especially the bottom end is very punchy and fast - also sound stage is very good. Stable as a rock even if you lose one supply rail - you will not fire speakers - there will be only small amount of DC at output (instead of chipamps for example).
In addition I installed small heat-sinks fors VA and CCS transistors, maybe they can do without them (approx 0,5W dissipation) -but it's better to be on the safe side.
 

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#309
osscar said:
In the last few months ab100 has become my everyday amplifier - I like everything, especially the bottom end is very punchy and fast - also sound stage is very good. Stable as a rock even if you lose one supply rail - you will not fire speakers - there will be only small amount of DC at output (instead of chipamps for example).
In addition I installed small heat-sinks fors VA and CCS transistors, maybe they can do without them (approx 0,5W dissipation) -but it's better to be on the safe side.
Click to expand...
🙂🙂🙂😀
 
#311
Thank you,
I know that it's been a while ... I've added the actual circuit of my amplifier.Of course, a lot of things can be changed according to the taste and possibilities :drink:
I think the amplifier is worth it to be built.
 

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#312
osscar said:
... I've added the actual circuit of my amplifier.Of course, a lot of things can be changed according to the taste and possibilities .
Click to expand...

I like your simplification of the output stage with the big darlingtons.

Have you built the amp both ways?

I can't get space heaters off my mind, but I should be looking into a Summer amp. I have plenty of AB commercial stuff, but the ones we build are so much better 🙂
 
#315
mpmarino said:
I

Have you built the amp both ways?
Click to expand...

No..just to3 version



richard_pc said:
Hello guys

As you know, the degeneration for differential input stage can greatly improve linearity,?

Thanks!
Click to expand...

I performed a quick simulation - with degeneration thd at high F getting worse..:Pirate:

regarding PCB:
I do not think someone has ordered a professional PCB for this amp - I only saw home made PCB and some nice PCB layouts in this topic.My PCB also is a "kitchen table" DIY for my needs and adapted to3 transistors.
 
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