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

[Stewart Pye]

Hi Tim,

Thanks. I was thinking insulating it would be a good idea.

Regards,
Stewart.

On 9/12/2015 9:26 AM, Tim Ressel wrote:
> 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
>>
>