PiezoDrive TD250 V8 User manual

TD250 V8 Manual 1 Rev 2, 31-09-2020
TD250 V8
Six Channel +/-250V Amplifier
Manual and Specifications

TD250 V8 Manual 2 Rev 2, 31-09-2020
Contents
1Introduction..................................................................................................................................... 3
2Warnings / Notes............................................................................................................................. 3
3Specifications................................................................................................................................... 4
4Delivery Contents ............................................................................................................................ 4
5Channel Configurations ................................................................................................................... 5
6Front Panel ...................................................................................................................................... 6
7Rear Panel........................................................................................................................................ 7
8Grounding and Earthing .................................................................................................................. 7
9Breakout Box ................................................................................................................................... 8
10 Power Bandwidth ......................................................................................................................... 9
11 Pulse Currents............................................................................................................................... 9
12 Small Signal Frequency Response ............................................................................................... 10
13 Noise........................................................................................................................................... 11
13.1 Noise Spectral Density ......................................................................................................... 11
13.2 RMS Noise............................................................................................................................ 12
13.3 Typical Noise Waveforms..................................................................................................... 12
13.4 Noise Test Conditions........................................................................................................... 13
14 Overload Protection.................................................................................................................... 13
14.1 Status Signal......................................................................................................................... 13
14.2 Disable Command ................................................................................................................ 13
15 Driving Piezoelectric Tubes......................................................................................................... 14
16 Bridged Load Configuration ........................................................................................................ 16
17 Warranty..................................................................................................................................... 16

TD250 V8 Manual 3 Rev 2, 31-09-2020
1Introduction
The TD250 is an ultra-low noise, six-channel voltage amplifier with +/-250V output range. The six
channels can be ordered as either independent (TD250-SGL), or as three channels with non-inverting
and inverting outputs (TD250-INV), which are ideal for driving piezoelectric tube scanners. The
inverting configuration can also be used to obtain +/-500V with a bridged load.
The TD250 can drive unlimited capacitive loads such as piezoelectric tubes, stack actuators, standard
piezoelectric actuators, and bender actuators. Applications include nanopositioning, microscopy,
electro-optics, and vibration control.
The input and output connectors are industry standard 9-Pin D-Sub connectors. The amplifier is
supplied with two 90cm DSUB cables and two breakout boxes that include BNC connectors and plug-
in screw-terminals. OEM and customized versions are also available.
The TD250 Version 8 provides a number of improvements over previous hardware:
The enclosure contains no fans and generates zero mechanical noise,
Increased output current from 22 to 28 mArms,
Improved noise performance, particularly at low-frequencies,
Remote status monitoring and remote shutdown.
Example applications include:
Compatible Actuators
Piezoelectric tubes
+/-250V
Piezoelectric plates
and other actuators
+/-250V with a grounded load, or
+/-500V in bridged configuration
Two wire benders
+/-250V with one electrode grounded (six actuators), or
+/-500V in bridged configuration (three actuators)
Three wire benders
+/-250V on each electrode (3 actuators), or
up to +/-250V on 5 actuators + HV Bias.
2Warnings / Notes
This device produces hazardous potentials and requires qualified personnel
and observation of mandatory safety protocols. Do not operate the device
with exposed conductors.

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3Specifications
Electrical Specifications
Output voltage range
+/-250 V Six Channels
RMS current
28 mA
Peak current
100 mA
Gain
25 V/V
Slew rate
20 V/us
Signal bandwidth
25 kHz
Power bandwidth
15 kHz
Noise
61 uVrms (100 nF Load)
Protection
Short-circuit, temperature, under-voltage
Input impedance
1 MOhm
Output impedance
100 Ohm
Input connector
9 Pin D-sub Female
Output connector
9 Pin D-sub Female
Power Supply
15V, 3A Minimum
Mechanical Specifications
Environment
0-40 C (32-104 F) Non-condensing humidity
Dimensions
216 x 108 x 48 mm (8.5 x 4.3 x 1.9 in)
Weight
1 kg (2.2 lb)
4Delivery Contents
TD250 amplifier
Two breakout boxes with BNC connectors and plug-in screw-terminals
Two 90cm DSUB9 cables, Male-Male, with straight-through wiring
Universal power supply 90 Vac to 250 Vac, 15V 3A output
IEC C13 power cable, suited to the shipping destination

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5Channel Configurations
The TD250 can be ordered with six independent channels (TD250-SGL) or three non-inverting and
inverting pairs for driving piezoelectric tubes and bridged loads (TD250-INV). The connection
diagrams are shown below.
Figure 1. TD250 Channel configurations
25
Out1
In1
25
Out2
In2
25
Out3
In3
25
Out4
In4
25
Out5
In5
25
Out6
In6
25
Out1
In1
-25
Out2
25
Out3
In3
-25
Out4
25
Out5
In5
-25
Out6
Independent Outputs
TD250-SGL
Non-Inverting and Inverting Outputs
TD250-INV

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6Front Panel
The input and output connectors are 9-pin DSUB receptacles. The recommended mating connectors
are 9-pin DSUB male cable plugs. The connector pins on the amplifier are listed below.
Figure 2. Front view of amplifier connector numbering
Connector Pin
Input Connector
Output Connector
1 to 6
Inputs 1 to 6
Outputs 1 to 6
7
Signal Ground
Signal Ground
8
Status
Signal Ground
9
Disable
Signal Ground
Connector shield
Chassis Earth
Chassis Earth
Table 1. Front panel D-sub connector pin-out
Input Signals
The standard input voltage is +/-10V and the absolute maximum input voltage is +/-20V. Use the
signal ground not chassis earth. The input impedance is 1 MOhm when the amplifier is powered on
and approximately 1.5 kOhm when the amplifier is off. For the inverting configuration (TD250-INV),
only inputs 1, 3 and 5 are active.
Disable Input
Applying a positive voltage of between 3V and 5V to the disable pin on the front panel connector will
turn off the amplifier. The input impedance is approximately 2 kOhm. The absolute maximum input
voltage is +/-10V.
Status Output
A +5V output (relative to signal ground) on the status pin indicates that the high-voltage power
supplies are both active and not effected by any overload or disable conditions. The output
impedance is 100 kOhm. The output voltage can be reduced to 3V by shunting the output to signal
ground with any 3V Zener diode.
Output Signals
The load should be connected between each output and signal ground. Do not operate the amplifier
with exposed conductors.
Status Indicator
Green indicates that the amplifier is on and the high-voltage power supply is active. Red indicates
that the amplifier is on but the high-voltage power supplies are less than 240V due to a fault
condition. A mixture of red and green indicates that the amplifier is on the verge of overload.
1
2
3
4
5
6
8
7
9

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7Rear Panel
The rear panel includes a chassis earth connector that can be used to improve shielding, particularly
when using an alternative power supply with an isolated output. This connector will accept a wire lug,
4mm plug, or stripped wire. The negative terminal of the power input connector is also connected to
the chassis. Since the negative output terminal of the included power supply is connected to earth,
the chassis is normally earthed.
The included power supply is Meanwell GST120A15-R7B. The power input connector is CUI PD-40S,
which suits a 4-pin DIN male plug,
8Grounding and Earthing
The chassis ground of the TD250 is electrically connected to the negative terminal of the power
supply inlet. The negative terminal of the included power supply (GST120A15-R7B) is internally
connected to earth, which earths the chassis of the TD250. The chassis can also be earthed by the lug
on the rear panel, which is required if an isolated AC power supply is used.
The input signals should be connected between an input pin (pin 1-6) and signal ground (pin 7). The
load should be connected between an output pin (pin 1-6) and signal ground (pin 7-9). The BNC
connector grounds are normally connected to chassis ground, and hence earth.
Figure 3. TD250 Chassis and signal ground configuration
Signal ground
AC-DC
Signal
Chassis ground
TD250

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9Breakout Box
The TD250 is supplied with two identical breakout boxes that simplify input and output connection
when using BNC cables or free wires. The header installed in the breakout box (Amphenol
OQ1032510000G) suits a 10-Way 3.81mm plug-in screw terminal (Amphenol TJ1031530000G) which
is also supplied (but not pictured below)
Each breakout box is connected to the amplifier with a 9-Pin male-male D-sub cable with one-to-one
(straight through) wiring.
Figure 4. Front and rear views of the breakout box
DSUB9 Connector Pin
BNC
Plug-in Screw Terminals
1 to 6
1 to 6
Outputs 1 to 6
7
BNC Shields
7
8
8
9
9
Grounded shield
10
Table 2. Breakout box connectivity

TD250 V8 Manual 9 Rev 2, 31-09-2020
10 Power Bandwidth
The power bandwidth is the maximum frequency sine wave that can be reproduced with a given
amplitude and load capacitance. An online tool is available for this purpose. The example screenshot
below shows that the maximum frequency is 650 Hz, with a 0.1 uF load and 200 Vpk-pk output.
Figure 5. Screenshot of online power bandwidth calculator (available here)
11 Pulse Currents
The peak current output of the TD250 is 100 mA. When reproducing step voltage changes in
capacitive loads, the peak current will remain above 85 mA for approximately 100 us. The relationship
between output current and duration is plotted in Figure 6.
Figure 6. Peak current duration for the TD250.

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12 Small Signal Frequency Response
The small signal bandwidth of the TD250 is approximately 25 kHz with a capacitive load less than
10 nF. For capacitive loads larger than 100 nF, the -3dB bandwidth is approximately

 

where is the load capacitance. The bandwidth for a range of capacitive loads is listed in Table 3. The
small signal frequency response is plotted for a range of load capacitances in Figure 7.
Figure 7. Small signal frequency response for a range of load capacitances

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13 Noise
13.1 Noise Spectral Density
The noise density of the TD250 for a range of load capacitances is plotted in Figure 8. The noise
density is approximately 0.45 , with a first order low-pass response, where the bandwidth is
inversely proportional to load capacitance.
The total white noise of the TD250 is equivalent to the voltage noise of a 20 kresistor at the input.
Since the equivalent input voltage noise of the TD250 is 18 , the noise of any driving source
should preferably be below 5 n, to avoid degrading performance.
The noise spectrum contains small periodic components at approximately 35 kHz and 70 kHz, which
arise from the power supply circuit. The amplitude of these narrowband components are significantly
smaller than the white noise, as observed in the time-domain plots in Section 13.3.
Due to the extremely low noise of the TD250, ground-loops between the TD250 and driving
instruments should be minimized. A ground loop effectively creates a large single turn coil, where any
stray magnetic fields will induce a small 50 Hz or 60 Hz voltage that is added to the signal. In cases
where large ground loops cannot be avoided, contact PiezoDrive for advice on minimizing
interference using isolation.
In critical piezoelectric positioning applications, other techniques are available to reduce positioning
noise levels. These applications are dealt with on a case by case basis depending on the application
requirements.
Figure 8. Output noise density for a range of load conditions in 

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13.2 RMS Noise
The RMS output voltage noise is listed in Table 3 for a range of load capacitances. Larger capacitances
result in smaller bandwidth and hence, smaller RMS noise.
Load Conditions
RMS Noise
-3dB Bandwidth
No Load
144 uV
26 kHz
1 nF
149 uV
28 kHz
3 nF
144 uV
26 kHz
10 nF
128 uV
17 kHz
30 nF
93 uV
5.3 kHz
100 nF
61 uV
1.6 kHz
300 nF
37 uV
5.3 kHz
1 uF
22 uV
1.6 kHz
3 uF
13 uV
530 Hz
10 uF
8 uV
160 Hz
Table 3. Typical output voltage noise and bandwidth versus load capacitance
13.3 Typical Noise Waveforms
An example of typical output voltage noise waveforms is plotted in Figure 9 for a range of load
capacitances. All cases share the same noise density but the reduced bandwidth with larger
capacitances results in smaller RMS noise, as listed in Table 3.
Figure 9. Typical noise waveforms for load capacitances ranging from 10nF to 10uF

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13.4 Noise Test Conditions
The output noise of the TD250 was measured with the standard DSUB cables and breakout boxes (as
supplied). All inputs on the input breakout box were directly connected to signal ground using the
screw terminal connector. A test capacitor was connected between the output of interest and ground
using the screw terminals on the breakout box. The output voltage was directly connected to a
SRS560 low-noise amplifier with a gain of 1000 and bandwidth of 0.03 Hz to 1 MHz. This signal is of
sufficient amplitude that it can be recorded with an oscilloscope and spectrum analyser.
14 Overload Protection
The overload protections mechanisms are listed below:
Overload
Behaviour
Indicator
Peak current
Short circuit
If the peak current limit is exceeded for any reason,
the output current is limited to 14 mA DC.
None –distorted
waveform
Average current
If the RMS output current is exceeded for more than
10 ms, the output current will be limited to 14 mA
DC or 28mA RMS.
None –distorted
waveform
Total current
The internal high-voltage supply is limited to a total
current limit of 60 mA average and 300 mA peak. If
this is exceeded, the supply voltage will be reduced.
Status signal drops below
1V and front panel LED
glows red
Temperature
If the heatsink temperature exceeds 70 C, the high-
voltage supply will be disabled until the
temperature reduces.
Status signal drops below
1V and front panel LED
glows red
Table 4. Overload conditions and behaviour
14.1 Status Signal
The Status signal on the front panel connector is nominally 5V during normal operation. The Status
signal drops below 1V when either of the HV supplies drop below 240V due to a fault condition. The
output impedance of this signal is 100 kOhm, it should be measured with a high impedance.
If the Status signal is pulled low due to a fault condition or disable command, the front panel LED
glows red. During startup, the LED will glow red for approximately 1 s.
14.2 Disable Command
Applying a positive voltage of between 3V and 5V to the disable pin on the front panel connector will
turn off the amplifier. The input impedance is approximately 2 kOhm. The absolute maximum input
voltage is +/-10V.

TD250 V8 Manual 14 Rev 2, 31-09-2020
15 Driving Piezoelectric Tubes
Piezoelectric tube scanners are thin cylinders of radially poled piezoelectric material with four
external electrodes and a continuous internal electrode. When a voltage is applied to one of the
external electrodes, the actuator wall expands which causes a vertical contraction and a large lateral
deflection of the tube tip. A circumferential electrode can be used for vertical or radial extension and
contraction. Piezoelectric tube scanners are used extensively in scanning probe microscopes and
applications such as fibre stretching and beam scanning. Read more online.
Figure 10. Piezoelectric tube with a fixed base and free end (full details)
When the base of the tube is fixed, the tip translations  and  are approximately [1]
  


  



where  and  are the and axis deflection, is the piezoelectric strain constant, is the
length of the tube, is the outside diameter, is the tube thickness, and 
and  are the electrode
voltages, which are applied oppositely to either side of the tube.
The vertical elongation due to a voltage applied on all four quadrants is
   

The diameter expansion due to a voltage applied on all four quadrants or the internal electrode is
  
The expansion range in the vertical and radial directions can be doubled by driving the internal and
external electrodes with opposite voltages, so long as the maximum permissible voltage is not
exceeded.
The TD250 is optimized for driving piezoelectric tube scanners in applications that require lowest
possible electronic and mechanical noise. Although many configurations are possible, the driven
internal electrode configuration shown in Figure 11 provides the maximum X, Y and Z travel range [1].

TD250 V8 Manual 15 Rev 2, 31-09-2020
This configuration is also referred to as the “Full Length” configuration [1]. The performance of this
method is compared to other configurations in reference [1].
In the driven internal electrode configuration, the X and Y electrodes are driven in the standard way
with equal and opposite voltages, as shown in Figure 11. By applying a negative voltage to the
internal electrode, a contraction equal to half the vertical scan range can be obtained. That is, the
vertical deflection is
  



where 
is a strictly negative voltage applied to the internal electrode.
This method exploits the higher positive electric field strength of the piezoelectric material, which is
usually five times the negative electric field strength. Care must be taken not to apply positive
voltages to the internal electrode since this can lead to depolarisation. For example, when using a
non-inverting channel, the input is enforced to be negative as shown in Figure 11. Alternatively, an
inverting channel can be used and the input is enforced to be positive.
Figure 11. Driving piezoelectric tubes with the TD250-INV (driven internal electrode configuration)
Piezoelectric tubes with prewired connections are available from PiezoDrive. Prewired tubes can also
be supplied with D-sub connectors for direct connection to the TD250 output cable.
References
[1] Electrode Configurations for Piezoelectric Tube Actuators with Improved Scan Range and Reduced
Cross-Coupling; D. S. Raghunvanshi, S. I. Moore, A. J. Fleming, and Y. K. Yong; IEEE/ASME Transactions
on Mechatronics, 2020, Available Online.

TD250 V8 Manual 16 Rev 2, 31-09-2020
16 Bridged Load Configuration
To obtain an output voltage range of +/-500V, the TD250-INV can used with a bridged load, as
illustrated below. Note that the negative side of the load is now driven and cannot be connected to
ground. The voltage across the bridged load is
   
where  is the voltage applied to inputs 1, 3, or 5 and has a maximum value of +/-10 V.
In the bridged configuration, the power bandwidth can be assessed by using the full peak-to-peak
load voltage in the calculator.
Figure 12. Bridged load configuration for obtaining +/-500V.
17 Warranty
The TD250 is guaranteed for 12 months. The warranty does not cover damage due to misuse.
25
Out1
In1
-25
Out2
25
In3
-25
25
In5
-25
TD250-INV
Out3
Out4
Out5
Out6
Load 1
Load 2
Load 3