Fri May 23 23:44:40 EDT 2014
Thermally coupled NPNs
Not to forget that a multi dac still this needs one NPN per channel,
best matched in temperature. So probably also a multi-transistor
array. Where to get those? Something like a CA3081 array? Or
CA3046. Some newer parts like DMC50601 or one of the NXP dual
transistors BC846, BC847.
Other: MPQ3906, MMPQ2907A, MMPQ3904 (4x - multi chip?).
One that stand's out is THAT300, mouser distributes.
Multi arrays are expensive or and duals are not very useful. It might
be better to stick with standard components and find a way to couple
them in temperature.
What about using power transistors instead? They can be hooked to a
heatsking much easier.. Cheapest NPN in TO-220? TIP31C ($0.2).
They're not cheap either.. Probably best to find thermal glue.
EDIT: There's also the TI LM3046 which is a replacement of the
CA3046. Together with some duals for current mirrors this is the
solution I'm looking for: one of the transistors can be used to
produce a DAC V_REF, with 4 remaining as EIDAC channels.