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periblepsis
periblepsis
20:46
@AHX123 Either with or without the diff pair (long-tailed) as the input stage, the same thing matters. You must get the output stage right, first. So stick with that. I've achieved very good THD in simulation. But that doesn't mean I'll get the same results when I pull parts out of a box and build it.
What it does mean that if I work at it with real parts then there's a much better chance that I can get something useful when it comes time to build it. But get me right about this -- that does NOT mean I can IGNORANTLY build something from simulation and expect good results.
That's because the moment I use real parts I experience reality -- genuine truth. And while the circuit may be in the ballpart of where it needs to be, adjustments will be required to deal with part variation in the actual parts I grab and use.
So I need to know what's important and what to look for, once it is built and power is applied. What should I measure? What should I expect to measure there? How do I adjust things to get what I need there? Etc.
In the output stage, I'll tend to want to see about 15-20% of the maximum peak current into the load passing through the emitter degeneration resistors. And I will also want that to be producing about 150-300 mV across both of them at once. You can measure the voltage differences across those resistors and, knowing their values, work out the current, too. Both facts must be simultaneously correct. Not just one of them.
So this may mean changing the resistor values themselves. Or it may mean changing the bootstrapped resistors at the series chain of the diodes and resistors behind the output transistors. Or it may mean inserting (or changing) the resistor value that is in series with the diodes. (Or I may need to change to a VBE multiplier, depending on what I see there.)
@AHX123 You have to know what you need and why you need it.
AHX123
AHX123
21:10
Yes, I completely understand where you are coming from I intend to do all of these. I was just asking an opinion from different people and figured out I wasn’t allowed to. I’ve already made some changes to the circuit with the quiescent current and the emitter degeneration resistors and I’ve reduced the midpoint voltage to about 6.3v.
Thank you for another Explanation and I’ll continue to make amendments to the circuit before I start building

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