The block shown by Figure 1 can be used to maintain constant current across an SMA in the range from few milliamperes to 3 A. The resistor, according to the desired current, is calculated by the following formula:
R = 1.25 / I
Where
R = resistance of R in ohm
I = desired current in the SMA
Other constant current sources described in this section can be used. In particular, we recommend MEC131E, which uses a common bipolar transistor for the task.
Figure 1 Constant current source.
