Tantalum capacitors

[lecto]

Tantalum capacitors are MAINLY used in electronics for
A) large capacitance smoothing circuit
B) tuned circuits
C) very high frequency circuits
D) alternating current circuits.
Which answer is best here?

 

[Ian Rogers]

I would say 'C' as tant's are used in TV and satellite signals (as previously mentioned)

 

[JimB]

Sorry Barney, but you are very wrong!

JimB

 

[Ian Rogers]

What would you suggest, JimB .. I wouldn't use tant's in an alternating circuit and I dont think you would use them in a tuned circuit!!


Right!! JimB I stand corrected...Slow not fast, applications Ive seen these in.. video recorders and sat receivers but this must be for stability not signaling

I apologize Lecto! I don't use them personally as they didn't seem to last for me..

 

[Sceadwian]

Tuned circuits.

 

[crutschow]

Tantalums are a type of polarized electrolytic capacitor and are used where you need a high value of capacitance. Thus the best answer is A.

The are generally not suitable for high frequency or tuned circuits.

 

[colin55]

You only have to be careful not to allow the voltage to rise above the specified value for the tant as they very easily go short-circuit.

 

[RCinFLA]

Answer A, used for power supply filter caps.

Usually low voltage portable devices but tantalum is more expensive then aluminum electrolytics. Recently very high K dielectric ceramic caps are replacing electrolytics in portable equipment since they are cheaper then elctrolytics and have lower ESR. Issue with the very high K dielectric ceramic cap is their capacitance is a function of average DC bias voltage (lower capacitance at higher end of rated voltage).

 

[JimB]

To expand a bit on my short post earlier,
although tantalum capacitors are found in TVs and satellite receivers, their use is usually restricted to supply decoupling.
They are certainly not used at high frequencies or in tuned circuits.

I recently needed a coupling capacitir in an audio circuit and picked a recycled (used) tant from my junk box.
The circuit worked OK but it was very noisy. The problem was the tantalum capacitor, I dont know if it was faulty as such or if it was just plain noisy due to small leakage currents, but it was not fit for purpose in my circuit. I replaced it with a small low value aluminium electrolytic which I was able to squeeze into the available space.

JimB

 

[Nigel Goodwin]

To expand a bit on my short post earlier,
although tantalum capacitors are found in TVs and satellite receivers, their use is usually restricted to supply decoupling.

They are only VERY rarely found in TV's and Satellite receivers, their poor reliability led to them been dropped decades ago.

Back when they were used, they were PSU decouplers - and commonly went S/C (very frequently).

They were also used in a couple of old Grundig TV's for the tuning of the frame oscillator - they went S/C there as well

 

[crutschow]

They are only VERY rarely found in TV's and Satellite receivers, their poor reliability led to them been dropped decades ago.

Tantalums may have been unreliable back then but now we use them for power supply decoupling and filtering in the high rel satellite systems my company builds. Of course the voltage rating is de-rated about 50% to help the reliability. No aluminum electrolytics are used due to their larger size and poorer reliability.

 

[ericgibbs]

I dont have problems with tantalum's, never use them close to their rated max voltage.
They do tend to be 'noisy' and a little 'leaky', but for general usage, no problem.

 

[Nigel Goodwin]

Tantalums may have been unreliable back then but now we use them for power supply decoupling and filtering in the high rel satellite systems my company builds. Of course the voltage rating is de-rated about 50% to help the reliability. No aluminum electrolytics are used due to their larger size and poorer reliability.

The tantalum capacitors that failed in HUGE numbers were normally 25V rated, and working on regulated 12V rails - so unreliable all TV manufacturers dropped them completely after a couple of disasterous years.

Good quality electrolytics are extremely reliable, it's the cheap junk ones which fail

 

[RCinFLA]

The old Spraque 'Orange Drop' tantalum caps had a metal migration problem with the positive outside solder termination shorting to inner tantalum block through the coating of orange epoxy that thinned in the corners during the coating dipping. They tried to use the same dipping process they used for their mylar caps. The higher the DC voltage the worse the metal migration problem. Just a bad design.

Square epoxy block tantulum caps (black or yellow colored) have isolated solder pads, with the metal solder pad spot welded to positive terminal post. These are very reliable. There are also Mil spec hermetic sealed tantalum in metal cans that are very reliable.

Tantalum electrolytics have lower ESR at higher frequencies compared to Aluminum electrolytics.

They go 'boom' more violently compared to 'fizzle' for aluminum when reverse polarity or over voltage is applied.

 

[Sceadwian]

I've taken apart several equalizers that used tantalum caps, hence my tuned circuit responce.

 

[Ian Rogers]

So the answer is A.....
ha ha...

These things shouldn't be called tantalums... they should be called tantrums cos they have caused a riot here.

Ian

 

[Sceadwian]

They always do Ian, Nigel seems to think they're the a sign of the apocalypse if used in a circuit and that they're never used, even though they're still used for new designs in devices such as advanced medical and space applications where reliability is critical. This is not the first post about Tantalums.

 

[Nigel Goodwin]

They always do Ian, Nigel seems to think they're the a sign of the apocalypse if used in a circuit and that they're never used, even though they're still used for new designs in devices such as advanced medical and space applications where reliability is critical. This is not the first post about Tantalums.

I just go with the facts - tant's were used for a very short period in TV's and domestic electronics - all domestic manufacturers dropped their use due to their extreme failure rate.

Interesting that RDinFLA may have explained the reason for their been so poor.

 

[Sceadwian]

Yes Nigel, as that is absolutely fascinating as it was a drop problem from some number of years ago... Keep clinging to the previous failures where aeronautical and aerospace industries are using what you consider a failed use component as high reliable and mil spec components now... They know what we didn't then.

**broken link removed**
https://www.electro-tech-online.com/custompdfs/2011/05/smtanmil.pdf

Anyone wishing to further research this will find at least another half dozen makers of high reliability tantalum capacitors.

 

[Nigel Goodwin]

Yes Nigel, as that is absolutely fascinating as it was a drop problem from some number of years ago... Keep clinging to the previous failures where aeronautical and aerospace industries are using what you consider a failed use component as high reliable and mil spec components now... They know what we didn't then.

The TV and domestic electronics manufacturers still don't use them though!.

Are perhaps only military grade ones any good?.