[sdiy] UA726 clone possible?

[Tom Bugs]

Thanks Mike -- that is great to know - the datasheet on the LS site 
hadn't said it was available in SOT23 form..
[Micross are good to deal with too]

Now..
What Tom was saying about 'exact dimensions' - I think I tend to agree 
with the idea that something roughly that size would be perfectly apt.
For one, lining up the exact pin arrangement (36 deg rotations) is not 
something I've attempted before in Eagle.
- I guess people must use actual uA726s with sockets anyways? What type 
of sockets are generally used? Are their specific circular ones that 
people tend to use?

I did sketch things roughly to 0.4" sqr. size and could actually fit the 
SO8 LS318 in on one side (just) - bit tough on space the other side for 
the Rs, Qs and ZDs.
Must probably rethink things a little from  my usual component types:
Rs - usually I use 0805 -> 0603 was my first idea, but maybe I'll go the 
next down (though DIY work may then be hard - though these'd surely be 
stuffed by machine)
- perhaps the 10ohm resistor needs to have some current handling 
capability though?
Qs - I think the BC847BS - again SOT23-6 form --- plenty of others to 
try but I have those already in Eagle. So would only require 3 of these 
pairs (plus the LS318)
ZDs - I've generally used SOT23s and occasional SOD80s - both seem kind 
of large here.. I saw at mouser they have one line of 0603 types 
(Bourns, i think)

So.. still doesn't seem impossible to at least get a test design done.

Ta,Tom

On 09/09/2015 16:46, Mike Gorman wrote:
> I've just checked on the Micross site and they have the LS318 in SOT23 and TO71 packages as well as SOIC and PDIP, so this device may still fit in a reasonably small package.
>
> Regards
>
> Mike
>
> On 9 Sep 2015, at 14:46, Jarno Verhoeven at ziggo.nl <jarno.verhoeven at ziggo.nl> wrote:
>
>> You can only get LS318 in SOIC, ideally you get something in a smaller case, for
>> it to fit the TO-can packaging.
>> There's BCM847bs/ds, but the matching isn't as good as LS318 (they do have them
>> in PNP, and NPN/PNP (the latter not matched)). Does anybody know of similar
>> parts, like DMMT3904?
>>
>> Jarno.
>>
>>
>>
>>> Op 9 september 2015 om 15:21 schreef Tom Bugs <admin at bugbrand.co.uk>:
>>>
>>>
>>> Sorry, please reply to this one so it has a new thread title:::
>>>
>>> ********************************
>>>
>>> I wondered before why no-one seems to have done a clone of the ua726.
>>>
>>> Doesn't *SEEM* all that complex?!
>>> A nice matched pair (eg LS318) is the main core.
>>> 6 transistors (I presume general purpose?), 2 x 6V2 zeners and 6
>>> standard resistors.. - those parts being for the heating element.
>>>
>>> Get the pin placement right, encapsulate it in goo..
>>>
>>> What am I wrong on?
>>>
>>> [I don't want to fully take on such a project, though could potentially
>>> do a design up for initial testing with a view to someone running a
>>> production in a friendly open-source-ish manner]
>>>
>>> Tom
>>>
>>>
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