LM385 ...

- F
- Fred Bartoli
  
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posted
15 years ago

Mon, Jan 5, 2009 9:52 PM

Speaking of LM385,

I've a nice app where its low bias current could shine (the adjust version with no internal divider) but the voltage ref is tied on cathode on the wrong side (I'd need the ref tied to anode).

No the TL431 won't work because of the huge 500nA max input bias. The LM385 max 35nA is much better and would be almost OK.

Anyone know of such a beast ?

Oh, and the footprint has to be ***tiny*** SOT23 would barely do. SC70 would be better. Oh and 125°C temp range with low bias on the range...

Relax, the voltage accuracy/drift isn't so important... But size is : (7mm dia PCB)

Maybe in my socks?

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Thanks,
Fred.

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- mook johnson
  
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posted
15 years ago

Tue, Jan 6, 2009 2:45 AM

what are your using it for. 1.24V reference?

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- Fred Bartoli
  
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posted
15 years ago

Tue, Jan 6, 2009 8:04 AM

mook johnson a écrit :

Opamp and offset reference, almost like the TL431 are used in SMPSs, but its for a really high impedance circuit, and with all the tricks exhausted I still do need LM385 style the low bias current. Given the allowed estate I'd even prefer a JFET/MOS input but it can't be, so...

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Thanks,
Fred.

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- Robert Baer
  
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posted
15 years ago

Tue, Jan 6, 2009 10:11 AM

STM has the TS431 where Vref is anode to adj pin; as of 2002 the smallest pkg was SOT23-5. National's LMV431 has ref anode to adj pin; as of 2005 the smallest pkg was SOT23-3. National's LM4040 was available in the SC70 package as of 2001 (fixed voltages). Hope this is of some help.