The M2 Output Stage in Class A/B, and maybe a Power WHAMMY?

Maximum ratings are without Operation...no current at the Output, no Input Signal...etc.

Operation ist what we want

The difference at the Pin V+ and V - is Always 36 v.

It does Not Matter If 36 in V + and gnd at V-
Or
18 v at Pin V+ and -18V at Pin V -
Difference is Always 36 v.
That is the max at this opv.

Voltages is the Potential difference between two Points.
 
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last one....realistic 3_ with 31V rail and standard BJT transistors simulated! (not build and tested)
setup is 13,8dB gain, 5,6Vpeak input needed.
maximum swing is 27,414V peak...not bad for a opamp LT 1793 with +/- 15Vrail

1732723267391.png


kr
chris
 

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Hi Master 😉 - Patrick

nope...i just played around with LT spice as a noob.
i know from my experience FX8 that with 31V and about 650mA a 4U/300 heatsink is just fine.

ps: to be honest,
i want to go ahead with my mooly amp but this bootstrapped triggered me😉
 
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if you have a strong PSU and a huge heat sink you get:

27,414Vpeak --> about 19,38Vrms--> into 8R load is about 47WATT. in 4R it is 94WATT.


a bit serious calculation 😉

8R - class A configuration possible:
19,38Vrms / 8R--> requests a current of 2,4A - so bias setup of 1,2A should be sufficient.
peak 27,414V / 8R --> requests a current of 3,42Amps peak
per MOSFET dissipation is about 30V and 1,2 A---> 36WATT maximum.

4R - Class AB configuration needed
19,38Vrms / 4R--> requests a current of 4,85A - each current 2,43A
peak 27,414V / 4R --> requests a current of 6,85Amps peak -each current 3,43A
STOP -
with about 30V on the MOSFET and 2,43A we get 72,67WATT on the MOSFET!!!!:flame:
 
So, in summary: Much better to keep to the originally intended 24 or perhaps 25V rails.

It would still be very nice to use the bootstrapped opa828 up front. I'm not understanding why you're not getting a similar gain to the opa604 at ±24V rails
 
e.g. 40W at 8R = 17,88Vrms ---> 17,88Vrms * 1,414 = 25,282Vpeak. That is the rail what you need....but...
with the sag of the PSU (high current is flowing) you have to add a sag of 4-7Volt.
lets take 5Volt.
so you needed DC voltage per rail is 30,282V---> 31Volt

so your transformer with 300VA and 24VAC should be right
24VAC after rectifier gives= 24VAC *1,414 (losses of diodes) = 31Volt

kr
chris
 
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