Micromechatronics, Inc. (MMech)

www.mmech.com - Ph: 814-861-5688

TD250 - Six Channel 250V Amplifier for Driving Piezo Tubes

Piezoelectric Drivers

TD250_LG

pdf-icon_sm TD250 Users Manual

keypad_sm Calculate Power Bandwidth PD200

Specifications:

Electrical Specifications
Output Voltage Ranges +/-250
RMS Current 22mA per channel
Peak Current 50 mA per channel
Gain 25 V/V
Slew Rate 30 V/us
Signal Bandwidth 50 kHz
Power Bandwidth 20 kHz (400 Vp-p sine-wave)
Max Power 25 W Dissipation
Load Stable with any load
Noise 70 uV RMS (100 nF Load)
Overload Over-current protection
Input Impedance
100 kOhms
Input Connectors BNC
Output Connector 9 Pin D-Sub
Power Supply 90 Vac to 250 Vac

Mechanical Specifications
Environment 0 - 40 C (32-104 F), Non-condensing humidity
Dimensions 275 x 141 x 64 mm (10.8 x5.5 x 2.5 in)
Weight 1kg (2.2 lb)

Features

The TD250 is an ultra-low noise, six-channel voltage amplifier with a bipolar 250V output range. The six channels can be driven independently, or configured as three channels with non-inverting and inverting outputs, which are ideal for driving piezoelectric tube scanners. The three-channel 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, vibration control, and piezoelectric motors.

The output connector is an industry standard 9-Pin D-Sub connector. A breakout board is also available which provides BNC connectors for each output and a plug-in screw-terminal connector. OEM and customized versions are also available.

Channel Configuration

The standard configuration for the TD250 is three non-inverting and inverting pairs for driving piezoelectric tubes and bridged loads, the order code for this configuration is TD250-INV. As illustrated below, the outputs can also be configured as six independent non-inverting channels, which has the order code TD250.

TD250-Config_lg

TD250 Channel Configuration

The front panel output connector is an industry standard 9-Pin Female D-Sub Connector (TE 3-1634584-2). Any Male 9-Pin D-Sub connector is compatible. The connector pinout is shown below.

TD250_Pinout_lg

Output Connector Pinout
Signal Pin
Output 1 5
Output 2 9
Output 3 4
Output 4 8
Output 5 3
Output 6 7
Ground 1,2,6

Driving Piezoelectric Tube Scanners

The voltage range, noise, and bandwidth of the TD250 have been optimized for driving piezoelectric tube scanners, for example the TB6009. Although many configurations are possible, the driven internal electrode configuration shown below is simple and provides the maximum X, Y and Z travel range. This configuration requires a tube with a continuous internal electrode and four external electrodes.

In the driven internal electrode configuration, the X and Y electrodes are driven in the standard way with equal and opposite voltages. By applying the full-scale negative voltage to the internal electrode, a contraction equal to half the vertical scan range is obtained. 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 risk depolarization if the tube voltage limit is less than ±500V, which is commonly true for tubes less than 1.2mm thick.

TD250_Tubes_lg

Driving piezoelectric tubes

Another common electrode configuration uses a separate circumferential electrode for the Z axis. This electrode is driven by a single channel with the full bipolar range.

In larger piezoelectric tubes, it is possible to quarter the external and internal electrodes. The internal electrodes can be either grounded or driven in the bridged configuration. Since the bridged configuration doubles the voltage difference across the piezo material, the thickness can also be doubled which significantly improves the resonance frequency. The disadvantages of this method include increased wiring and fabrication difficulty.

Bridged Load Configuration

To obtain an output voltage range of +/-500V, the TD250-INV can used with a bridged load, as illustrated below.

TD250_Bridged_lg

Bridged configuration using TD250-INV

In the bridged configuration, the power bandwidth can be assessed by using the full peak-to-peak load voltage in the calculator, or by doubling the effective capacitance.

Power Bandwidth

With a capacitive load, the peak load current for a sine-wave is Formula_1

where Vpp is the peak-to-peak output voltage, C is the load capacitance, and f is the frequency. Given a peak current limit Ipk, the maximum frequency is therefore Formula_2. However, the TD250 is protected by both peak and average current limits. The average current Iav+ is defined as the average positive or negative current. For example, for a sine-wave Formula_3

Therefore, for a sine-wave Formula_4_2 Since the average current limit of the TD250 is Iav+=0.26, the maximum frequency sine-wave, or power bandwidth of the TD250, is equal to  Formula_4

The above result is true for any periodic waveform such as a triangular signal. The RMS current for a sine-wave can also be related to the average current, Formula_5

The power bandwidths for a range of load capacitance values are listed below.

Load Peak to Peak Voltage
Cap 200V 300V 400V 500V
No Load 50 kHz 33 kHz 25 kHz 20 kHz
3 nf 12.0 kHz 8.3 kHz 6.2 kHz 5.0 kHz
10 nf 4.5 kHz 3.0 kHz 2.2 kHz 1.8 kHz
30 nf 1.6 kHz 1.0 kHz 800 Hz 640 Hz
100nf 490 Hz 330 Hz 240 Hz 190 Hz
300nf 160 Hz 110 Hz 83 Hz 66 Hz
1uf 50 Hz 33 Hz 25 Hz 20 Hz
Power bandwidth versus load capacitance

In the following figure, the maximum frequency periodic signal is plotted against the peak-to-peak voltage.

TD250_PowerBandwidth_lg

Power bandwidth versus voltage and load capacitance
TD250_FRF_lg
Small signal frequency response
Load Cap. Bandwidth
No Load 100 kHz
3 nF 39 kHz
10 nF 14 kHz
30 nF 5.1 kHz
100 nF 1.5 kHz
300 nF 520 Hz
1 uF 150 Hz
Small signal bandwidth versus load capacitance (-3dB)

Noise

The output noise contains a low frequency component (0.03 Hz to 20 Hz) that is independent of the load capacitance; and a high frequency component (20 Hz to 1 MHz) that is inversely related to the load capacitance. Many manufacturers quote only the AC noise measured in the 20 Hz to 100 kHz range, which is usually a gross underestimate.

The noise is measured with an SR560 low-noise amplifier (Gain = 1000), oscilloscope, and Agilent 34461A Voltmeter. The low-frequency noise is measured to be 50 uV RMS with a peak-to-peak voltage of 300 uV. This noise level is less than the resolution of a state-of-the-art 24-bit digital-to-analog converter.

The high frequency noise (20 Hz to 1 MHz) is listed in the table below versus load capacitance. The total noise from 0.03 Hz to 1 MHz can be found by square summing the RMS values, that is

Load Cap. Bandwidth HF Noise RMSTotal Noise RMS
No Load 100 kHz 130 uV 139 uV
3 nF 39 kHz 80 uV 94 uV
10 nF 14 kHz 50 uV 71 uV
30 nF 5.1 kHz 30 uV 58 uV
100 nF 1.5 kHz 40 uV 64 uV
300 nF 520 Hz 50 uV 71 uV
1 uF 150 Hz 70 uV 86 uV
RMS noise versus load capacitance (0.03 Hz to 1 MHz)

Overload Protection

Each channel is independently protected against average and peak current overload. Exceeding these limits will result in signal distortion. The front-panel overload indicator will illuminate when the total power supplied to all channels is greater than 25W. This can occur when all channels are simultaneously operated at full power or when there is a failure of one or more channels. During a maximum power overload, the power supply is temporarily disabled and will reset once the power drops below 25W. When the amplifier is first turned on, the overload protection circuit is engaged by default and will require approximately two seconds to reset.

Breakout Box / Cables

The breakout box provides BNC connectors for each output and a plug-in screw-terminal connector (Amphenol 20020004-D081B01LF). The breakout box connects to the amplifier via an included 75cm male-male 9-Pin D-Sub cable.

Order Code: TD250-Breakout

TD250_BreakOut_1000w_lg

TD250 Breakout box
TD250_ScrewTerm_med
Plug-in screw terminal connector

A number of 300 V D-Sub cables are available for the amplifier. All are supplied with at least one 9-Pin D-Sub connector for connecting to the amplifier. The second connector is either a D-Sub connector for connecting to the breakout box, or free wires.

Connector 2 Length Order Code
9 Pin Male 75 cm DSUB9-MM-75cm
9 Pin Male 150 cm DSUB9-MM-150cm
Free Wires 75 cm DSUB9-MW-75cm
Free Wires 150 cm DSUB9-MW-150cm
9 Pin D-Sub cables
TD250_Cable_med
9 Pin male-male D-Sub cable
Signal Color
Output 1 Yellow
Output 2 Grey
Output 3 Orange
Output 4 Purple
Output 5 Red
Output 6 Blue
Ground Brown, Green, Black
Cable Wire Color

Enclosure

The TD250 enclosure has a side air intake and rear exhaust. These vents should not be obstructed.

TD250_Dims_lg

TD250 Dimensions

Warranty

PiezoDrive amplifiers are guaranteed for a period of 3 months. The warranty does not cover damage due to misuse or incorrect user configuration of the amplifier.

More Information

200 Innovation Blvd. Suite 155
State College, PA 16803, USA
Ph: (814)-861-5688
Fax: (814)-861-1418
contact@mmech.com
MMechLogosm