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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[2]?  Or
CA3046.  Some newer parts like DMC50601[3] or one of the NXP dual
transistors BC846, BC847[4].

Other: MPQ3906, MMPQ2907A, MMPQ3904[5] (4x - multi chip?).

One that stand's out is THAT300[6], mouser distributes[7].

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[8].

EDIT: There's also the TI LM3046[9] 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.

[1] http://www.linear.com/parametric/Digital-to-Analog_Converters_%28DAC%29#!cols_1049,1050,1056,1054,2234,1059,1031,1367!s_1050,1!gtd_!1049_%3E=12!1054_Serial%20SPI
[2] https://www.futurlec.com/Linear/CA3081Npr.shtml
[3] http://www.digikey.com/product-search/en?mpart=DMC506010R&vendor=9
[4] http://www.nxp.com/products/bipolar_transistors/general_purpose_bipolar_transistors/general_purpose_transistors/double_transistors/
[5] http://www.fairchildsemi.com/pf/MM/MMPQ3904.html
[6] http://www.thatcorp.com/300-series_Matched_Transistor_Array_ICs.shtml
[7] http://de.mouser.com/thatcorporation/
[8] http://www.newark.com/arctic-silver/aata-5g/adhesive-thermal-syringe-5g/dp/71T6886?CMP=KNC-GPLA
[9] http://www.ti.com/lit/ds/symlink/lm3046.pdf



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