General > General Technical Chat
BJTs being phased out?
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tszaboo:

--- Quote from: EEVblog on October 15, 2020, 10:01:41 am ---
--- Quote from: Benta on October 13, 2020, 08:17:09 pm ---I'm much more worried about the JFET, which is a dying species.
--- End quote ---

I'm feeling a Save the JFET T-Shirt coming on...

--- End quote ---
We really should! Otherwise how do we make current mirrors to reflect on society.

OP: BJT is cheaper than MOSFET so its not going anywhere.
tooki:

--- Quote from: coppice on October 15, 2020, 04:56:23 pm ---
--- Quote from: bsfeechannel on October 15, 2020, 04:46:58 pm ---
--- Quote from: Benta on October 14, 2020, 10:26:54 pm ---Today, only specialty manufacturers such as linearsystems.com supply a comprehensive line of JFETs, like the famous 2SJ74/2SK170.
Like I said, it's a dying species.

--- End quote ---
There's a discrete JFET inside every single electret microphone capsule. Maybe it is becoming a product for niche applications.

--- End quote ---
True, but MEMS microphones are killing the market for electret microphones.

--- End quote ---
Is that true outside of severely space-constrained applications like cellphones and the mikes built into phone earpieces (be it inline in the cord or integrated like in AirPods)? I haven't gotten the impression that any other applications have embraced MEMS mikes.
coppice:

--- Quote from: tooki on October 15, 2020, 06:20:47 pm ---
--- Quote from: coppice on October 15, 2020, 04:56:23 pm ---
--- Quote from: bsfeechannel on October 15, 2020, 04:46:58 pm ---
--- Quote from: Benta on October 14, 2020, 10:26:54 pm ---Today, only specialty manufacturers such as linearsystems.com supply a comprehensive line of JFETs, like the famous 2SJ74/2SK170.
Like I said, it's a dying species.

--- End quote ---
There's a discrete JFET inside every single electret microphone capsule. Maybe it is becoming a product for niche applications.

--- End quote ---
True, but MEMS microphones are killing the market for electret microphones.

--- End quote ---
Is that true outside of severely space-constrained applications like cellphones and the mikes built into phone earpieces (be it inline in the cord or integrated like in AirPods)? I haven't gotten the impression that any other applications have embraced MEMS mikes.

--- End quote ---
That's 99% of all mics, isn't it? The electret mic market was mostly phones and cell phones. Phones have almost gone. Cellphones have moved to MEMS mics. Most other mics are condenser or dynamic. There were once some very high quality electret mics, but they seem to have gone, and now we only have condenser, ribbon and dynamic mics for high quality applications. Condenser mics also use a JFET, but their volumes are millions, not the hundreds of millions we see with cellphones.
tooki:

--- Quote from: coppice on October 15, 2020, 06:31:46 pm ---
--- Quote from: tooki on October 15, 2020, 06:20:47 pm ---
--- Quote from: coppice on October 15, 2020, 04:56:23 pm ---True, but MEMS microphones are killing the market for electret microphones.

--- End quote ---
Is that true outside of severely space-constrained applications like cellphones and the mikes built into phone earpieces (be it inline in the cord or integrated like in AirPods)? I haven't gotten the impression that any other applications have embraced MEMS mikes.

--- End quote ---
That's 99% of all mics, isn't it?

--- End quote ---
In terms of sheer unit sales, perhaps. But other applications (like recording, stage and PA mikes, the ones in voice recorders, webcams, etc.) are hugely important and aren't going anywhere.
tooki:
Second reply after you edited to add everything that follows the single sentence quoted above.



--- Quote from: coppice on October 15, 2020, 06:31:46 pm ---The electret mic market was mostly phones and cell phones.

--- End quote ---
Uhhhh… electret mikes were in practically every tape recorder. They're still widely used in webcams, laptops, and all manner of audio devices. They're still in every landline or VOIP phone and headset.


--- Quote from: coppice on October 15, 2020, 06:31:46 pm ---Phones have almost gone.
--- End quote ---
At home, yes, they're going that way. In businesses, not really. They may not be true circuit-switched landline phones any more, they're VOIP, but they still use handsets with electrets. Call center style headsets also use electrets.


--- Quote from: coppice on October 15, 2020, 06:31:46 pm ---Cellphones have moved to MEMS mics.

--- End quote ---
Yes, I think we established that! ;)


--- Quote from: coppice on October 15, 2020, 06:31:46 pm ---Most other mics are condenser or dynamic. There were once some very high quality electret mics, but they seem to have gone, and now we only have condenser, ribbon and dynamic mics for high quality applications. Condenser mics also use a JFET, but their volumes are millions, not the hundreds of millions we see with cellphones.

--- End quote ---
That is categorically untrue. Electrets are still omnipresent in pro audio such as broadcast TV. Because of the poor performance and longevity of early electrets, pro audio distanced itself from the word "electret" and just calls them condenser mikes, because electrets are a subtype of condenser mikes. (It simply means a condenser mike that is pre-polarized, as opposed to ones that need external polarization power.) As such, I think it's eminently possible that a significant percentage (perhaps even a majority?) of "condenser" mikes are actually electret condensers. (In pro audio, you'll see reference to "true condenser" to try and signify an externally polarized condenser mike, even though that phrase is technically imprecise since it attempts to mislead one into thinking that electrets aren't truly condenser mikes.)

For example, the Sennheiser MKE 2 is a $350 lavalier microphone. In a spec sheet, Sennheiser describes it as a "pre-polarized condensor [sic] microphone". And "pre-polarized" is literally the definition of an electret, so it means it's an electret mike in actuality.


Again, I don't dispute that the billions of cheap mikes in cellphones and cellphone accessories have largely moved to MEMS, but to claim that the electret is dead is, well, dead wrong.
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