[sdiy] I have found that SSM2210 transistor arrays give better performance in my latest oscillator design.

[Ian Fritz]

At 10:37 AM 6/24/2006, Ray Wilson wrote:

>To any who have bought my Music From Outer Space PC boards for VCOs I have 
>discovered that the SSM2210 transistor array gives better performance than 
>the LM394. The LM394 while good is left behind by the SSM2210. The SSM2210 
>allows more octaves of tracking.


Hi Ray --

That's an interesting result; thanks for letting us know about it.  There 
hasn't been all that much work on directly comparing different pairs.

According to my notes, I measured the Rbe of the LM394 to be 1.0 Ohm.  The 
SSM2210 is speced at 0.3 Ohm -- a factor of 3 better!

Still, with my 394-based saw VCO I was able to get tracking to within 0.1% 
up to 28 kHz.  1 Ohm of Rbe isnt all that much to compensate.  Do you have 
any numbers as to what your tracking error is in the two cases?

One difference I see between our designs is that your current at 10 kHz is 
~0.5 mA whereas mine is more like 0.1 mA.  So you have a factor of 5 more 
error from Rbe.  Perhaps that's why you see better tracking with the 2210?

Regards,

   Ian

http://home.earthlink.net/~ijfritz/sy_cir2.htm