jean_claudeabeille wrote:
I uploaded the new corrected one along with the missing components files :
AmpJCA.zip.
I hope that this time the schematic is correct.
Still has errors.
Still missing the LF353. LTspice is looking for the schematic symbol (.asy
file).
Needs a statement to include the special "standard.bjt" file.
Meanwhile I received 2 models of mps4250. Simulations with one of them and
with BC557
give very different results. Which one is true ?
Probably both ... or neither.
Remember all components have tolerances, which for some transistor
parameters can be on the order of +/-100% or so (well, +100%, -50%, or
more).
In fact results are very dependent of model's parameters.
That's unfortunate. A good amplifier design ought to make the results
largely independent of model parameters, over a reasonable range.
Besides, I don't know if it's important but on my amp, U2 is CNY17-4 which
is not present in LTSpice's OPTOS.
As long as you include a model for the CNY17-4, it's OK.
What I woud like to understand is HOW to equilibrate the voltages at the
collectors of Q12 and Q13 to get quite the same current at R101 and R111.
Here's where the discussion becomes off-topic for this forum, because we
are now talking about amplifier design, rather than circuit simulation.
One would use the trimmer 1K resistor to set the quiescent (static)
currents through R101 and R111.
To get equal currents through R101 and R111, that should happen
automatically. As long as no current goes out to the load, all the current
through R101 flows through R111. To get no quiescent current to the load,
trim the input offset voltage so that the output pin sits at 0V when the
input is 0V.
Regards,
Andy
