[sdiy] op amp based filter

[Oren Leavitt]

cheater cheater wrote:
> Ah, I just mentioned 101 since it's the one Wikipedia mentions in the
> op amp article. I do realize that 201/301 are similar, they all share
> the same datasheet. But yeah, it was just an example. But I wasn't
> able to find the 201 or 301 anywhere for 'normal' money either. Well,
> 4 usd isn't that bad, but if you can get something similar for sub-1
> usd and with good shipping costs..
> 
> Cheers,
> D.
> 
> On Sat, Jul 24, 2010 at 19:02, Roy J. Tellason, Sr.
> <rtellason at verizon.net> wrote:
>> On Saturday 24 July 2010 12:08:21 pm cheater cheater wrote:
>>> On the other hand, maybe an op amp with an external capacitor could
>>> work? I understand LM101 is one such design but I was unable to find a
>>> place to buy them *cheap*. National has them at around $4, that
>>> doesn't look encouraging, but maybe someone owns a huge heap of NOS.
>>> As a bonus you can have them in metal can format.
>> Do you understand that the "101" part is military temperature range?  The 201 and 301 are much more common,  the 301 particularly,  and probably a whole lot easier to find,  not to mention cheaper...
>>
>>
>> --
>> Member of the toughest, meanest, deadliest, most unrelenting -- and
>> ablest -- form of life in this section of space,  a critter that can
>> be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
>> -
>> Information is more dangerous than cannon to a society ruled by lies. --James
>> M Dakin


Electronic Goldmine has LM301 - $0.49
http://www.goldmine-elec-products.com/prodinfo.asp?number=G32103

Allied, DigiKey, Mouser stock LM301 for less than a buck.

The 301 being an externally compensated device, should offer some 
options to play with in this design.
Pin 1 provides access to the point between the input stage and the 
voltage gain/output stage.

Using high gain, will likely multiply the influence of stray 
capacitances too. How you construct it may affect the end result.

Wire something together and keep us posted!
- Oren