electrolytic caps VS. tantalum caps - Electronic Circuits Projects Diagrams Free

hardcore misery · 2nd January 2007, 08:51 AM

which is better in high frequency operation?
or in high-gain pedals like BOSS metalzone

**Nigel Goodwin** · 2nd January 2007, 09:15 AM

Quote:

Originally Posted by hardcore misery

which is better in high frequency operation?
or in high-gain pedals like BOSS metalzone

I wouldn't recommend tantalums for anything, they are far too unreliable!.

gramo · 2nd January 2007, 09:43 AM

Not sure about that, esp when high frequencies are concerned, heres an extract from http://www.engineersedge.com/instrum...capacitors.htm

Quote:

There are numerous advantages to using tantalum capacitors over other types of capacitors. First, tantalum capacitors have a higher volumetric efficiency (CV/cc) when compared to other types of capacitors. For instance, a 10-microfarad tantalum capacitor can replace a 100-microfarad aluminum capacitor. Tantalum capacitors are easily mounted onto circuit boards, and give engineering designers the ability to place these components in closely-confined printed circuit board space, as well as utilizing tantalum capacitors' excellent power dissipation characteristics. Second, tantalum capacitors have superior frequency characteristics than many other types of capacitors, including aluminum electrolytics. A comparable CV tantalum capacitor has an ESR ten times better than an aluminum electrolytic capacitor. Third, tantalum capacitors are highly reliable – electrical performance qualities do not degrade over time. Tantalum capacitors do not lose capacitance unlike electrolytic capacitors – in fact, the shelf life for tantalums is regarded as unlimited. Fourth, tantalum capacitors don't wear out – in fact, if there is an imperfection in the dielectric layer of a tantalum, the resistance of the manganese dioxide layer will typically convert to a form that is even more resistive. The new oxide form plugs up the faulty region and results in a reduction in current flow. Finally, tantalum capacitors have an excellent wide operating range, from –55 degrees Centigrade to +125 degrees Centigrade, with a minimal amount of degradation in electrical properties throughout this range.

dknguyen · 2nd January 2007, 10:08 AM

Tantalums are better than electrolytics for high frequency, but electrolytics are cheaper and can come in much larger sizes.

**Nigel Goodwin** · 2nd January 2007, 10:38 AM

They were only ever used for a small number of years in domestic electronics, their huge failure rate caused all manufacturers to stop fitting them. Personally the only place I'd consider using one is as the timing capacitor on a 555 - where their lower leakage is a great advantage.

eng1 · 2nd January 2007, 11:30 AM

In fact they don't tolerate voltage peeks and may explode if their ratings are exceeded. On the other hand, they are more precise, stable and suitable for higher frequencies. I've recently used tantalum capacitors after LDO regulators because of their low ESR.

Oznog · 2nd January 2007, 12:15 PM

Quote:

Originally Posted by Nigel Goodwin

They were only ever used for a small number of years in domestic electronics, their huge failure rate caused all manufacturers to stop fitting them. Personally the only place I'd consider using one is as the timing capacitor on a 555 - where their lower leakage is a great advantage.

I'm not sure what you're saying. Tantalums have been the capacitor of choice for many years and are used almost exclusively in many consumer electronics products. Their size is the primary advantage, like the description says, not only is a cap in a similar voltage and capacitance much smaller, but due to the lower ESR the tantalum can often be of a much smaller capacitance. MP3 players are almost all tant. Hard drives, tants.

In fact a big issue is that tantalum only comes from one part of the world, a somewhat unstable part at that, and most electronics depend so heavily on tant caps that it's become a real concern. Awhile back I saw they were working hard to develop vanadium caps as a substitute for tantalum primarily due to supply issues.

**Nigel Goodwin** · 2nd January 2007, 01:01 PM

Quote:

Originally Posted by Oznog

I'm not sure what you're saying. Tantalums have been the capacitor of choice for many years and are used almost exclusively in many consumer electronics products.

Just checked six different TV's, from a brand new LCD one to one 12 years old - can't see a single tantalum capacitor in any of them. In fact I've not seen any since the late 70's early 80's when they were dropped because of their poor reliability. Also just checked a digital satellite receiver, a DVD player, a 40Gb HDD, and a PC motherboard - none in those either.

I've not seen them used for over 20 years!.

Oznog · 2nd January 2007, 02:24 PM

Quote:

Originally Posted by Nigel Goodwin

Just checked six different TV's, from a brand new LCD one to one 12 years old - can't see a single tantalum capacitor in any of them. In fact I've not seen any since the late 70's early 80's when they were dropped because of their poor reliability. Also just checked a digital satellite receiver, a DVD player, a 40Gb HDD, and a PC motherboard - none in those either.

I've not seen them used for over 20 years!.

Generally don't show up as often in non-space-critical items like a TV, they're a bit more expensive. I have several recent hard drives I just had in front of me and most had tants. Are you sure you even know what they look like now?

Also tants fit in SMD pkgs better. Electrolytics are still generally cans which is sort of an awkward to turn into an SMD as well as being a tall profile. Tants are usually a flat construction and fit into some common sizes of rectangular SMD pkgs.

Now remember what you saw 20 yrs ago is not a permanent state of tech. Come on, you know this. Don't be the grampa who talks about how color TV picture tubes go out too soon because he saw them do that in the early days. Tech doesn't work like that. A product can easily be unreliable or impractical for a few years and then totally change.

Fact is tants are actively being used in LOTS of stuff. They've been the hot component that is essential for miniaturization and the industry has successfully embraced it for many years! There are no really problematic "gotchas" to them, at least not for the past 5 years. Can't say why you're not seeing them in the items you have picked up, but you gotta look around- they're used, and they're used in lots of stuff!

**Nigel Goodwin** · 2nd January 2007, 02:37 PM

Quote:

Originally Posted by Oznog

Generally don't show up as often in non-space-critical items like a TV, they're a bit more expensive. I have several recent hard drives I just had in front of me and most had tants. Are you sure you even know what they look like now?

Also tants fit in SMD pkgs better. Electrolytics are still generally cans which is sort of an awkward to turn into an SMD as well as being a tall profile. Tants are usually a flat construction and fit into some common sizes of rectangular SMD pkgs.

Hard to tell with SM components, but the only ones I've had occasion to check are listed as SM Electrolytics - NOT as Tantalum. However, perhaps they are tantalum, and listed wrongly in the manufacturers literature? - it would certainly explain why they fail and require changing!

Quote:

Now remember what you saw 20 yrs ago is not a permanent state of tech. Come on, you know this. Don't be the grampa who talks about how color TV picture tubes go out too soon because he saw them do that in the early days. Tech doesn't work like that. A product can easily be unreliable or impractical for a few years and then totally change.

Agreed, but the manufacturers don't seem to want to get bitten again, as I say, I don't really see any.

chemelec · 2nd January 2007, 03:01 PM

I use Thousands of tantalums in my projects and have Never had one fail. (Unless Connected in Backwards by Mistake)

But Most important is to know "Where" and "Where-Not" to use them.

They were never ment to be a Blocking Capacitor for AC Signals.

As Bypass Caps on "Voltage Requlators", they are the BEST.

But they are NOT the Only cap you should use here as they are Not ment for Brute Force Filtering.
(Generally speaking they should be placed Directly across the input and Output of the actual regulator IC, Thus Complimenting the supply of the additional Electrolytic filter caps.)

They also work very well for Bypassing IC Supplies, Directly across the IC's Supply Pins.

Oznog · 2nd January 2007, 03:03 PM

Actually electrolytics themselves bit mfgs about 5 yrs back. One of the big Asian mfgs of components supposedly stole a formula for electrolytics but only got part of the formula. Bad caps saturated the industry and nobody knew. Those caps went into most of the motherboards for quite a while. Then they all started to go out, caps leaking crap all over. I have a prime example.

Look on Digikey, the ratio of hits for electrolytics to tants is about 2:1. Note that tants cover a more limited range- there are no high voltage or super-high capacity tants, so fewer types are expected. But you gotta see that 7400+ types available doesn't indicate a product line that failed years ago!

You'll also find in many spec sheets (for a regulator for example) they specify "low ESR electrolyic or tantalum type". Sometimes they say if you don't use a tantalum you may need a ceramic in parallel with an electrolytic to meet both the ESR and capacitance spec. That's sort of half-assed when you think about it. The ceramic has a low ESR but only a capacity of like 0.1uF at best which only counters high freq ripple. A tant has low impedance for all of its capacitance.

I've used plenty of tants in my projects. They do work well and I've only had one fail because it was in backwards. I greatly prefer them for their small size and low ESR.

I have heard not to use a tant for a continuous voltage of more than like half the peak voltage rating. I am unsure how universal that recommendation is. I mean that may or may not have been true for one mfg, but is it true for all the technology? I don't see this in cap spec sheets. I do see 16v as a popular voltage, yet I have to note that there are few 8v circuits out there that would justify its popularity. And that's too far off to be intended for regulated 5v circuits. It suggests people might be using these for a regulated 12v line to me.

**Nigel Goodwin** · 2nd January 2007, 03:10 PM

Quote:

Originally Posted by chemelec

They also work very well for Bypassing IC Supplies, Directly across the IC's Supply Pins.

That's where they used to fail, most of them were used as supply decouplers on large PCB's, scattered all over the board. They invariably failed S/C, making the faulty one VERY difficult to find.

Oznog · 2nd January 2007, 03:11 PM

Oh hey I found this neat formula that estimates tant reliability:

LT=LR*(ER/EO)^3*2^(deltaT/10)

Where:
LT = failure rate under stated temperature and voltage
LR = the failure rate at rated limits
ER = rated voltage limit
E O = operating voltage
deltaT = difference between rated operating temperature and actual capacitor temperature in C

eng1 · 2nd January 2007, 03:14 PM

You may see some SMD tantalum capacitors on PC soundcards, for example.

That formula might be good only at DC? It doesn't consider frequency. And the maximum voltage of a capacitor is specified at DC.

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2nd January 2007, 08:51 AM	#1
hardcore misery	electrolytic caps VS. tantalum caps which is better in high frequency operation? or in high-gain pedals like BOSS metalzone

2nd January 2007, 10:08 AM	#4
dknguyen	Tantalums are better than electrolytics for high frequency, but electrolytics are cheaper and can come in much larger sizes.

2nd January 2007, 10:38 AM	#5
Nigel Goodwin	They were only ever used for a small number of years in domestic electronics, their huge failure rate caused all manufacturers to stop fitting them. Personally the only place I'd consider using one is as the timing capacitor on a 555 - where their lower leakage is a great advantage. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

2nd January 2007, 11:30 AM	#6
eng1	In fact they don't tolerate voltage peeks and may explode if their ratings are exceeded. On the other hand, they are more precise, stable and suitable for higher frequencies. I've recently used tantalum capacitors after LDO regulators because of their low ESR.

2nd January 2007, 03:01 PM	#11
chemelec	I use Thousands of tantalums in my projects and have Never had one fail. (Unless Connected in Backwards by Mistake) But Most important is to know "Where" and "Where-Not" to use them. They were never ment to be a Blocking Capacitor for AC Signals. As Bypass Caps on "Voltage Requlators", they are the BEST. But they are NOT the Only cap you should use here as they are Not ment for Brute Force Filtering. (Generally speaking they should be placed Directly across the input and Output of the actual regulator IC, Thus Complimenting the supply of the additional Electrolytic filter caps.) They also work very well for Bypassing IC Supplies, Directly across the IC's Supply Pins. __________________ I No Longer accept Private Messages on here. All Emails to me Must Contain the Word \"Electronic\" in the \"Subject Line\" or they go Directly to my Junk Mail Folder. Email me at: chemelec@hotmail.com Website: http://www3.telus.net/chemelec

2nd January 2007, 03:03 PM	#12
Oznog	Actually electrolytics themselves bit mfgs about 5 yrs back. One of the big Asian mfgs of components supposedly stole a formula for electrolytics but only got part of the formula. Bad caps saturated the industry and nobody knew. Those caps went into most of the motherboards for quite a while. Then they all started to go out, caps leaking crap all over. I have a prime example. Look on Digikey, the ratio of hits for electrolytics to tants is about 2:1. Note that tants cover a more limited range- there are no high voltage or super-high capacity tants, so fewer types are expected. But you gotta see that 7400+ types available doesn't indicate a product line that failed years ago! You'll also find in many spec sheets (for a regulator for example) they specify "low ESR electrolyic or tantalum type". Sometimes they say if you don't use a tantalum you may need a ceramic in parallel with an electrolytic to meet both the ESR and capacitance spec. That's sort of half-assed when you think about it. The ceramic has a low ESR but only a capacity of like 0.1uF at best which only counters high freq ripple. A tant has low impedance for all of its capacitance. I've used plenty of tants in my projects. They do work well and I've only had one fail because it was in backwards. I greatly prefer them for their small size and low ESR. I have heard not to use a tant for a continuous voltage of more than like half the peak voltage rating. I am unsure how universal that recommendation is. I mean that may or may not have been true for one mfg, but is it true for all the technology? I don't see this in cap spec sheets. I do see 16v as a popular voltage, yet I have to note that there are few 8v circuits out there that would justify its popularity. And that's too far off to be intended for regulated 5v circuits. It suggests people might be using these for a regulated 12v line to me. __________________ I thought what I'd do was I'd pretend I was one of those deaf-mutes.

2nd January 2007, 03:11 PM	#14
Oznog	Oh hey I found this neat formula that estimates tant reliability: LT=LR(ER/EO)^32^(deltaT/10) Where: LT = failure rate under stated temperature and voltage LR = the failure rate at rated limits ER = rated voltage limit E O = operating voltage deltaT = difference between rated operating temperature and actual capacitor temperature in C __________________ I thought what I'd do was I'd pretend I was one of those deaf-mutes.

2nd January 2007, 03:14 PM	#15
eng1	You may see some SMD tantalum capacitors on PC soundcards, for example. That formula might be good only at DC? It doesn't consider frequency. And the maximum voltage of a capacitor is specified at DC. Last edited by eng1; 2nd January 2007 at 03:17 PM.