PD200X4 V2 Manual
16
Modified 13/01/2021
15
Bias Outputs and Piezo Benders
The bias outputs are labelled HV+ and HV- on the front-panel screw terminals. The output voltages
are fixed at the maximum output voltages of the amplifier, and are not affected by the voltage limit
potentiometers. For example, a PD200X4-V100,100 (with a +/-100V output range) will 100V
and -100V on HV+ and HV- respectively. For amplifier configurations where the HV- output is zero
(e.g. PD200X4-V0,200), it is preferable to use ground rather than the HV- output. If specialized bias
voltages are required, an amplifier output channel can be used with a DC offset.
The bias outputs provide a small DC output current of approximately 30mA; however, they can
source or sink large AC currents, and are ideal for generating bias voltages for piezoelectric actuators,
which only require AC current. Bender actuators can be driven with a single or dual bias voltage.
The most common bender actuators are parallel-poled and driven using the ‘biased unipolar’ or
‘three-wire’ configuration [1], as shown in Figure 9.
Figure 9. Parallel-poled bender driven in the biased unipolar configuration [1].
A zero volt input results in +150V across the top piezo layer and maximum upward deflection. A 7.5V
input results in +150V across the bottom piezo layer and maximum downward deflection. The
deflection
𝛿
can be represented by
𝛿 =
𝑉
𝑖𝑛
− 7.5/2
7.5
𝛿
𝑝𝑝
where
𝛿
𝑝𝑝
is the peak-to-peak displacement of the bender.
To reduce the maximum DC voltage, a negative bias voltage can be used, as shown in Figure 10.
Figure 10. 200V Parallel-poled bender driven with dual bias sources.
+150 Vdc
𝛿
Parallel-poled bender, e.g.
Thorlabs PB4NB2W or
PiezoDrive BA6020
Ground
PD200X4-V0,150
HV+
CH1 Out
Ground
CH1 In
0 to +150V
0 to 7.5V
+100 Vdc
𝛿
200V parallel-poled bender,
e.g. Noliac CMBR02
-100 Vdc
PD200X4-V100,100
HV+
CH1 Out
HV-
CH1 In
+/-100 V
+/-5V
