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

[Tim Ressel]

I looked into using a MAT04 and a THAT 300 for the AN299 design. It 
looked like it should work okay.

You don't need much heating, especially if you figure out a way to 
insulate the package. In my original AN299 VCO I used a dip package and 
a wire wrap socket to raise the 3046 above the board, then made a 
styrofoam coffin that fit over the assembly. that worked well.

--tr

On 9/11/2015 3:21 PM, Stewart Pye wrote:
> Hi Tom,
>
> The THAT300 is a 4 NPN transistor array. I think there is also a MAT 4 
> tranny array that Rick mentioned earlier.
>
> I've designed (on paper) a VCO that uses the THAT300 for expo 
> converter with sensor and heater. I'm planning on laying out the PCB 
> this weekend. I probably should breadboard it first, but I like living 
> on the edge! I asked THAT some questions about the maximum dissipation 
> and they were quite helpful. If you're interested I can email the 
> reply to you. Since the max Vce and Vcb voltages are 36V (compared to 
> 15V for the LM3046) you can set it up so you have a higher Vce when 
> the heater is on, so you can dissipate more power with the same current.
>
>
> Regards,
> Stewart.
>
>
>
>
> On 9/11/2015 8:26 AM, Tom Bugs wrote:
>> Well, yes, it is a learning project driven by curiousity rather than 
>> particular need & hopefully I can get some learnings along the way..
>> My understanding is that the CA/LM3046 has lower specs for the 
>> matched pair than the LS318 (or similar AD NPN pairs) - though of 
>> course it has been used in a heater arrangement in quite a few 
>> commercial synths over the years.
>> I would think that the heater element needs to produce a stable 
>> temperature (somewhere above ambient) and this temperature needs to 
>> be efficectively coupled to the matched pair - I would hope that as 
>> long as the device is potted (or using the heat transfer epoxy 
>> compound I have) this will be sufficient.
>> It could equally be possible to have all components on one side and 
>> have the PCB overhang the ua726 footprint (the current design already 
>> does a little).
>> Cheers, Tom
>>
>>
>> On 10/09/2015 22:54, Richie Burnett wrote:
>>>> 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.
>>>
>>> Isn't the whole idea of the uA726 that all of the components are 
>>> fabricated on the same silicon die so that they're always at the 
>>> same temperature? You're not going to get all the transistors at the 
>>> same temperature if they're plastic packaged devices soldered onto 
>>> different sides of an FR4 board.  Maybe I'm missing something here, 
>>> but it seems to me that you'd be better off starting with something 
>>> like a CA3046 transistor array where all devices are fabricated at 
>>> the same time on a common substrate.
>>>
>>> -Richie,
>>>
>>
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>

-- 
--Tim Ressel
Circuit Abbey
timr at circuitabbey.com