What's wrong with the plain old BJT current mirror?
i have never used them, but from what i have seen they have a very high tempco even if the transistor are matched, also very difficult to thermally couple them, and i still have to generate a Iref
I apologize, I had not read carefully the original post so I had not realized that the circuit is energized just .1s/60s so average power is 1/600
are you sure? is the thermal spread fast enough to allow them to survive that power peak? also, 0.1s over 60s is just a example, ill probably try to keep the on time as low as possible (just enough to allow the current source and the instrumentation amplifier to settle and read it with the ADC), and also reduce the off time, a more realistic figure would be 0.01s every 5s, but im not really sure yet.
ill probably just stick with 1206 resistor (0.25W), it should be more than adequate.
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Maybe an instrumentation amplifier is what you need. Something like the INA332?
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It's all in the datasheet (page 6). At 25ºC the TC is negative, and the deviation is about +0.3% to -0.2%. Some time ago I found these articles about current sources/sinks. The emphasis is on audio, but they provide a lot of information.
thanks for the links, ill watch them better this night.
anyway, thanks for the suggestion on the instrumentation amplifier, it is exacly what i was looking for
![Grin ;D](https://www.eevblog.com/forum/Smileys/default/grin.gif)
the INA332 has just a little problem: its supply voltage.
its 5V, and the segnal terminal come to Vcc + 0.5V (abs max), which is too low.
i have searched a bit by myself and i found the
ina826, which look intresting but it hasnt a enable pin
![Banging Head |O](https://www.eevblog.com/forum/Smileys/default/bangheadonwall.gif)
there are few things that i dont understand, for example, how the Vos of the ina relate to the output voltage? its just Vos x Gain like a normal op amp or what?
also, the minimium output voltage is 0.1V? (P 7, output section, right?)
then, given the fact that is not possible to have a reversed polarity on the resistor, its possible to use a mosfet to short (or not) a resistor in order to change the gain factor? in this way the minimium Vout wouldnt be a problem