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Voltage boosting an opamp

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Yansi:
It is not your issue to question what is or isn't viable for others. That kind of questioning is what indeed pisses me off. Either stay on topic and discuss the amplifier topology, or go away please.

This circuit is part of a much more complex project, where shaving $5 out of a BOM really counts.  Even if only 10 pieces of it would be made (I guess probably more will), $50 spared just on one amplifier is not an insignificant amount for a homegamer.

PCB area is a stupid argument anyway, as if space would be the constraint, I would probably not be going this route in the first place.

I have a lot more things to do, than just this amplifier that currently will not earn me any $, so please forgive me I still work on this project for more than 2 years.

SiliconWizard:
Jeez, just relax. If you don't want other people's opinions, don't use a public forum. This forum is not your playground where you set your own rules. When you open a thread, all kinds of people are going to give various opinions, and that's actually what makes it interesting and fruitful. If you're not interested in one opinion, you can just ignore it. And again *I* did not revive this thread, it got active again, and I reacted to it (was not even on the forum when it first started.) It's every user's right, as long as they are not insulting anyone. I don't think I did. But you did with your "stupid" words.

Threads in a public forum are not just a private discussion. If you wanted it to be private, just use private messages. Many other people looking for a similar solution can be interested in reading various options and opinions. Without counter-arguments, some people after reading it may conclude that using HV opamps is stupid whatever the context - which is obviously silly. Threads are shared discussions, not just a private and free tech support tool.

As to the time it took, I don't doubt (or care, it's your business) you had many other things to do, but it just shows designing a discrete version was definitely not as simple as it first looked, so considering other options was definitely not stupid engineering-wise. So I consider my point (which was short enough not to require hours to read) to be relevant. Again, take it or leave it, but it could help others deciding what's the best option for their own project.

Yansi:
Your solution is the same type, as if you would just say "buy a complete ready test instrument for the purpose", why making one. No thanks.

Now I politely ask you to leave this thread, as you did not contribute anything useful, rather just being provocative and nitpicking about what is or isn't expensive, which is not the topic this thread is about. Neither are you entitled to evaluate how much work something required to make. This is my thread and I make the rules.

Thank you for making mess out of this thread, no-one will be willing to read. Please leave. Bye.

magic:

--- Quote from: SiliconWizard on November 10, 2019, 05:23:08 pm ---Without counter-arguments, some people after reading it may conclude that using HV opamps is stupid whatever the context - which is obviously silly.
--- End quote ---
HV ICs is boutique stuff, only available at big distributors and pricey. I feel like people use them either because they are space/power constrained or because the knowledge how to whack together a simple analog circuit has largely been forgotten in the mainstream, due to the huge success of low voltage ICs which are indeed highly competitive both on performance and cost. I think I have seen examples of the latter.

Discrete still lives in some commercial power analog applications like audio. Here's one of the highest performance speaker amps out there. I can see a few ICs but they are in a sea of transistors, I think it's safe bet most of the high voltage signal path is discrete. Go tell those guys they should be using opamps :P

magic:
And speaking of the actual circuit...


--- Quote from: Yansi on November 10, 2019, 01:38:49 pm ---Just wondering, how could I get more stable biasing. Huh.  ???  What would be the dis/advantages of using 4 diodes vs. Vbe multiplier?

--- End quote ---
I'm not sure what bias instability you have, but if it decreases under heat, which is what it probably does, you should perhaps replace one pair of diodes with 680Ω resistors to match the tempco of the parallel branch.

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