[sdiy] [AH] Re: UA726 clone possible?

[Tom Bugs]

A little update::

LS/Micross seem confused about the LS318 package availability.. I've put 
in an order with Micross for a few SOT23 ones, but heard from LS that 
they don't actually do the LS318 in SOT23 (I emailed them to query as 
their datasheet didn't mention the SOT23)

Anyways, have managed to do a pretty compact test circuit - roughly 0.5" 
sqr(ish) with pins in a rough circle - matched pair on top and other 
components on the base.
Next time I order some proto PCBs I will add a few and see about 
building them up. At that point maybe I'll ask here for some people 
willing to run some tests with these 'chips'

Cheers, Tom

On 09/09/2015 18:35, Tom Bugs wrote:
> 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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>

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