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Not strictly true. You must ensure that the voltage rating of the part is higher than the voltage used in the circuit.
Of course, this is rarely a problem in low voltage (9v) circuits as most cap are rated higher than 9v.
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In a pedal it doesn't much matter as long as it's over the maximum applied voltage differential.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Yep low voltage Tantalum caps are very common now, especially in surface mount form as it's the smallest form factor for buck converter smoothing in laptops, tablet PC's etc ... and these to me seem about the most unreliable type of cap ever made, generally any dead short on a laptop board is a failed tantalum
Here's a question, an electrolytic cap needs a DC polarising voltage to work but how low can that voltage be ? I mean as an example I've got a circuit where I've temporarily had to use the wrong opamp, so I have a DC offset on the output of around 200mV. As a stop gap I've capacitor coupled the next stage and as it's a very low impedance I've had to use an electrolytic . I was unsure if the 200mV would suffice but it seems to be fine and the offsets gone after the cap .... just made me wonder how low the polarising could be ?
The general rule of thumb with electrolytics used to be that they needed to see at least a 1/3 their rated voltage to perform correctly.
As a result of this there was an aversion to employing electrolytic in circuits with no polarising DC voltage; however this position seems to have been refuted and you regularly see electrolytics as DC blocking caps in op-amp based circuits. Other than at turn on where the +/- rails might not come up evenly, there should be no voltage across the cap.
I'd agree with tants being shite.
The general rule of thumb with electrolytics used to be that they needed to see at least a 1/3 their rated voltage to perform correctly.
As a result of this there was an aversion to employing electrolytic in circuits with no polarising DC voltage; however this position seems to have been refuted and you regularly see electrolytics as DC blocking caps in op-amp based circuits. Other than at turn on where the +/- rails might not come up evenly, there should be no voltage across the cap.
I'd agree with tants being shite.
I did try tants recently when I was trying to trace a microscopic DC leak in a high-impedance circuit where there was a problem with charge buildup, but it made no difference. I wouldn't have bothered otherwise...
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Tants are used because they have low ESR which can be VERY important in higher frequency applications (eg switching mode power supplies), but pointless at audio.
Modern electrolytics are far better now in this regard than they used to be, but tants are still smaller so useful when PCB space is at a premium.
Tants have virtually no tolerance of reverse polarity.