TD250 V8
Six Channel +/-250V Amplifier
Manual and Specifications

TD250 V8 Manual1

Rev 2, 31-09-2020

Contents
1

Introduction ..................................................................................................................................... 3

2

Warnings / Notes ............................................................................................................................. 3

3

Specifications ................................................................................................................................... 4

4

Delivery Contents ............................................................................................................................ 4

5

Channel Configurations ................................................................................................................... 5

6

Front Panel ...................................................................................................................................... 6

7

Rear Panel........................................................................................................................................ 78Grounding and Earthing .................................................................................................................. 7

9

Breakout Box ................................................................................................................................... 8

10Power 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 Manual2

Rev 2, 31-09-2020

1 Introduction
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-invertingand 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 plugin 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.

2 Warnings / 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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3 Specifications
Electrical Specifications
Output voltage range+/-250 V Six Channels

RMS current

28 mA

Peak current

100 mAGain

25 V/V

Slew rate

20 V/usSignal bandwidth

25 kHzPower bandwidth

15 kHzNoise

61 uVrms (100 nF Load)

Protection

Short-circuit, temperature, under-voltage

Input impedance

1 MOhmOutput 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)

Weight1 kg (2.2 lb)

4 Delivery 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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5 Channel Configurations
The TD250 can be ordered with six independent channels (TD250-SGL) or three non-inverting andinverting pairs for driving piezoelectric tubes and bridged loads (TD250-INV). The connection
diagrams are shown below.
Independent Outputs
TD250-SGL
In1

25

Non-Inverting and Inverting Outputs
TD250-INV

Out1

25

Out1

In1
In2

25

Out2

-25

Out2

In3

25

Out3

25

Out3

In3
In4

25

Out4

-25

Out4

In5

25

Out5

25

Out5

-25

Out6

In5
In6

25

Out6

Figure 1. TD250 Channel configurations

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6 Front 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.

5

3

4
9

8

1

2
7

6

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

StatusSignal Ground9

DisableSignal 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 thesignal 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 willturn 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 indicatesthat 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.
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7 Rear 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 tothe 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,

8 Grounding 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 internallyconnected to earth, which earths the chassis of the TD250. The chassis can also be earthed by the lugon 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.
TD250
Signal

AC-DCSignal ground
Chassis groundFigure 3. TD250 Chassis and signal ground configuration

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9 Breakout 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) whichis 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

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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 incapacitive loads, the peak current will remain above 85 mA for approximately 100 us. The relationshipbetween 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
𝑓−3𝑑𝐵 =

1
628 𝐶

where 𝐶 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 uV/√Hz, with a first order low-pass response, where the bandwidth isinversely proportional to load capacitance.
The total white noise of the TD250 is equivalent to the voltage noise of a 20 kΩ resistor at the input.
Since the equivalent input voltage noise of the TD250 is 18 nV/√Hz, the noise of any driving source
should preferably be below 5 nV/√Hz, to avoid degrading performance.
The noise spectrum contains small periodic components at approximately 35 kHz and 70 kHz, whicharise 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 𝐕𝐫𝐦𝐬/√𝐇𝐳
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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 Load144 uV
26 kHz
1 nF
149 uV
28 kHz3 nF
144 uV
26 kHz
10 nF
128 uV
17 kHz30 nF
93 uV
5.3 kHz100 nF61 uV
1.6 kHz300 nF37 uV
5.3 kHz1 uF
22 uV
1.6 kHz
3 uF
13 uV
530 Hz
10 uF
8 uV
160 HzTable 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 (assupplied). All inputs on the input breakout box were directly connected to signal ground using thescrew terminal connector. A test capacitor was connected between the output of interest and groundusing 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 ofsufficient amplitude that it can be recorded with an oscilloscope and spectrum analyser.

14 Overload Protection
The overload protections mechanisms are listed below:
Overload
Peak current
Short circuit
Average current

Total current

Temperature

Behaviour

Indicator

If the peak current limit is exceeded for any reason, None – distorted
the output current is limited to 14 mA DC.
waveform
If the RMS output current is exceeded for more thanNone – distorted
10 ms, the output current will be limited to 14 mA
waveform
DC or 28mA RMS.
The internal high-voltage supply is limited to a total Status signal drops below
current limit of 60 mA average and 300 mA peak. If 1V and front panel LED
this is exceeded, the supply voltage will be reduced. glows red
If the heatsink temperature exceeds 70 C, the high- Status signal drops below
voltage supply will be disabled until the1V and front panel LED
temperature reduces.
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 willturn off the amplifier. The input impedance is approximately 2 kOhm. The absolute maximum input
voltage is +/-10V.

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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 theexternal electrodes, the actuator wall expands which causes a vertical contraction and a large lateraldeflection of the tube tip. A circumferential electrode can be used for vertical or radial extension andcontraction. Piezoelectric tube scanners are used extensively in scanning probe microscopes andapplications 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 Δ𝑥 and Δ𝑦 are approximately [1]Δ𝑥 = 𝑉𝑥2√2𝑑31 𝐿2
2√2𝑑31 𝐿2, Δ𝑦 = 𝑉𝑦𝜋𝐷ℎ𝜋𝐷ℎwhere Δ𝑥 and Δ𝑦 are the 𝑥 and 𝑦 axis deflection, 𝑑31 is the piezoelectric strain constant, 𝐿 is thelength of the tube, 𝐷 is the outside diameter, ℎ is the tube thickness, and 𝑉𝑥 and 𝑉𝑦 are the electrodevoltages, which are applied oppositely to either side of the tube.
The vertical elongation due to a voltage 𝑉 applied on all four quadrants is
Δ𝐿 = −𝑉𝑑31 𝐿ℎ

The diameter expansion due to a voltage applied on all four quadrants or the internal electrode isΔ𝐷 = 𝑉2𝑑33
The expansion range in the vertical and radial directions can be doubled by driving the internal andexternal electrodes with opposite voltages, so long as the maximum permissible voltage is notexceeded.
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].
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This configuration is also referred to as the “Full Length” configuration [1]. The performance of thismethod 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 theinternal electrode, a contraction equal to half the vertical scan range can be obtained. That is, thevertical deflection is
Δ𝐿 = 𝑉𝑧

𝑑31 𝐿ℎ

where 𝑉𝑧 is a strictly negative voltage applied to the internal electrode.
This method exploits the higher positive electric field strength of the piezoelectric material, which isusually 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.

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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
𝑉𝐿𝑜𝑎𝑑 = 𝑉𝑖𝑛 × 50
where 𝑉𝑖𝑛 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-peakload voltage in the calculator.
TD250-INV
25

Out1

In1

Load 1
Out2
-25

25

Out3

In3

Load 2
Out4
-25

25

Out5

In5

Load 3-25

Out6Figure 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.

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