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Application Note

AN1: Driving a Bipolar Deformable Mirror With a Unipolar HV Amplifier

The AmpArray[32]™ provides a unipolar 0V to +200V output range, because this range is well suited to the majority of commonly used MOEMS mirror technologies. Many other deformable mirrors, however, require a bipolar drive voltage to control them. For example, most of the popular bimorph mirrors require a bipolar voltage swing.

How can the unipolar AmpArray[32] be used to control a bimorph mirror?

If the negative side of all the mirror's actuators is connected to a common +100V d.c. bias voltage, the actuators now see a ±100V swing across them when a 0V to +200V signal is applied to the positive side of the actuators. The midrange (flat mirror) position is then at +100V drive signal, (i.e. at +5V input signal, for a 0V to +10V input range). As long as the actuators' common negative terminal is available at an external connector, this arrangement allows a bipolar signal to be applied to the mirror's actuators by a unipolar drive.

An asymmetric swing can be implemented by altering the value of the bias voltage.

The mirror must be rated for the voltage range to be applied. Remember that the +100V bias line carries the return a.c. drive current.

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