Re: Replacing tantalum capacitors with ceramic capacitors


vdonisa
 

I think LDO's are over used these days. They were "invented" for the specific purpose of powering low voltage high current circuits (5V or less). Let's say you need 3V of overhead for a classic regulator to work properly, and you power a 3.3V circuit - then you notice that you dissipate about the same power on the regulator as on the rest of the circuit! So here we go in a race to lower the voltage drop, at the expense of stability et all. Enter the LDO world.

I miss the good old days of +-15V circuits. With 18V transformers and 7815s, the regulators would dissipate just a fraction of the total power, stable and all. Not to mention that some of those good old +-15V op amps are unmatched in performance by their 5V single supply brethren.

Now why someone would use an LDO in a high voltage circuit totally beats me. I see it done regularly by audio aficionados replacing 78xx with LT1086 - probably on the belief that if it's newer and more expensive it must be better. A cursory look at the specs would show that they actually lose both on noise and stability.

---In TekScopes@..., <yachadm@...> wrote :

I learnt about the requirement for High-ESR caps in LDO circuits, the practical way.

About 10 years ago, I had just recapped an APC 2000VA UPS, which had required about 60 caps (Panasonic FM Low-ESR), and I was very proud of my work, as I stood back and admired it before switching on.

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