[time-nuts] 5>10 doubler

[Charles Steinmetz]

I wrote:

>>Once upon a time, Motorola made monolithic quad BJTs -- but I'm not 
>>aware of any matched quads similar to 2N2222s at this time.

Gerhard replied:

>There still are
>MAT04
>HFA3046-3096-3127-3128
>
>if duals are enough:
>SSM2220
>MAT12
>also mat02, mat03, maybe SSM2110 [probably meant SSM2210?  also, 
>there is SSM2212]

I had thought of these, but unfortunately, all of the AD parts (MAT 
and SSM) -- which otherwise look promising -- have reverse diodes 
across the B-E junctions, which rules them out as diode substitutes.

The HFA parts are small-geometry, ultra-high frequency devices (Ft = 
8GHz for the NPNs), not at all like 2N2222s.  It is doubtful they 
would have the low flicker noise of 2222s.  They are monolithic, so 
they should be pretty well matched, but only the differential pair in 
the 3046 is actually specified for matching -- and you couldn't use 
both of the diff pair in a ring structure because of the common 
cathodes.  The 3127 would be the part to try.  I have some, so maybe 
I'll try them (but I'm not hopeful).

Best regards,

Charles