PX200 – 140 Watt Voltage Amplifier

The PX200 is a high-power low-noise amplifier designed to drive unlimited capacitive loads from DC to 100 kHz. The output voltage range is user-selectable from +/-50V to +200V which provides a high degree of application flexibility. In particular, two amplifiers can be connected in bridge-mode to provide +/-200V with 280 Watts of power. The amplifier will deliver up to 4 Amps peak for sinusoidal operation, or up to 8 Amps for pulse applications.

The amplifier is compact, light-weight, and can be powered from any mains supply. The output connectors include LEMO 00, LEMO 0B, and 4mm Banana Jacks so many commercially available piezoelectric stack actuators can be directly connected. The PX200 is suited to a wide range of applications including: electro-optics, ultrasonics, vibration control, nanopositioning systems, and piezoelectric motors.

PX200 - 140W Voltage Amplifier
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Specifications

Electrical Specifications
Output Voltage Ranges +50V to +200V, +/-100V, -50V to 150V
RMS Current 1.5 Amps (3 Amps in 100V range)
Peak Current 2 Amps, 4 Amps, or 8 Amps
Gain 20 V/V
Slew Rate 35 V/us
Signal Bandwidth 390 kHz
Power Bandwidth 55 kHz (200 Vp-p sine-wave)
Max Power 140 W Dissipation
Offset 0V to Full Range with front panel adjustment
Load Stable with any load
Noise 270 uV RMS (10 uF Load, 0.03 Hz to 1 MHz)
Overload Thermal and over-current protection
Voltage Monitor 1/20 V/V (BNC)
Current Monitor 1 V/A (BNC)
Analog Input Signal input (BNC, Zin = 27k)
Output Connectors LEMO 0B, LEMO 00, 4mm Banana
Power Supply 90 Vac to 250 Vac
Mechanical Specifications
Environment 0 – 40 C (32-104 F), Non-condensing humidity
Dimensions 212 x 304.8 x 88 mm (8.35 x 12 x 3.46 in)
Weight 2 kg (4.4 lb)

Output Voltage Range

The desired voltage range should be identified when ordering. The following voltage ranges can be obtained with the correct combination of installed jumpers. Note that incorrect jumper settings may damage the amplifier.

The standard output voltage range is 0V to 200V. However, the amplifier can be supplied with any of the following voltage ranges by appending the order code with the voltage range code; for example, the standard configuration is PX200-V200. The voltage range jumper locations are labelled LK1 to LK8 on the PCB. Only three jumpers should be installed at any time.

Voltage Range RMS Current Code +Supply GND -Supply
0V to +200 1.5 A -V200 LK1 LK8 LK7
0V to +150 1.5 A -V150 LK2 LK8 LK7
-50 to +100 1.5 A -V50,100 LK1 LK3 LK6
-50 to +150 1.5 A -V50,150 LK1 LK5 LK7
-100 to +100 1.5 A -V100,100 LK1 LK3 LK7

200 Volt Range Configurations

In addition to the 200V ranges described above, three 100V ranges are also possible. These ranges have the benefit of twice the peak and RMS current, which enables higher frequency operation when driving low-voltage actuators.

Voltage Range RMS Current Code +Supply GND -Supply
0V to +100 3.0 A -V100 LK1 LK3 LK4
0V to +50 3.0 A -V50 LK2 LK3 LK4
-50 to +50 3.0 A -V50,50 LK2 LK3 LK6

100 Volt Range Configurations

The jumper settings can be modified by disconnecting the amplifier from mains power then removing the top panel to access the PCB board.

Output Current (200V Range)

In the 200V range, the standard output current is +/-2 Amps peak and 1.5 Amps RMS. This peak current is matched to the average current limit so that a sine-wave can be reproduced continuously at full current. However, for applications that require fast step changes in voltage, the amplifier can be configured in a pulse mode with 4 Amps or 8 Amps peak current limit. The maximum pulse time for each mode is listed and plotted below

The output current range can be configured by disconnecting the amplifier from mains power then removing the top panel. The following modes can them be obtained. The amplifier can be supplied preconfigured to any current range by appending the order code with the current range code, for example, the standard configuration is PX200-C2.

Peak Current Code Peak Limit LK17 Overload Timer Max Pulse Time
2 A -C2 LK11 “B” Position LK16 and LK18 Out 1 ms
4 A -C4 LK12 “B” Position LK16 and LK18 In 200 us
8 A -C8 LK13 “B” Position LK16 and LK18 In 100 us

Current Limit Configuration in 200V Range

px200 maximum pulse time versus current

Maximum pulse time versus current

Output Current (100V Range)

In the 100V range, the output current can be doubled to +/-4 Amps peak and 3 Amps RMS. For applications that require fast step changes in voltage, the amplifier can also be configured in a pulse mode with 8 Amps peak. The maximum pulse time is identical to the 200V range discussed above.

The output current range can be configured by disconnecting the amplifier from mains power then removing the top panel. The following modes can them be obtained. The amplifier can be supplied preconfigured to any current range by appending the order code with the current range code, for example, the 100V range and 4A current limit is PX200-V100-C4B.

Peak Current Code Peak Limit LK17 Overload Timer Max Pulse Time
4 A -C4B LK12 “A” Position LK16 and LK18 Out 1 ms
8 A -C8B LK13 “A” Position LK16 and LK18 In 100 us

Current Limit Configuration in 100V Range

Power Bandwidth

Power Bandwidth Calculator (200V Range)

Power Bandwidth Calculator (100V Range)

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

$$ I_{pk}=\pm V_{pp} \pi C f ,$$ where \(V_{pp}\) is the peak-to-peak output voltage, \(C\) is the load capacitance and \(f\) is the frequency. Given a peak current limit \(I_{pk}\), the maximum frequency is therefore \(f=I_{pk}/V_{pp} \pi C\). However, the PX200 is protected by both peak and average current limits. The average current \(I_{av+}\) is defined as the average positive or negative current. For example, for a sine-wave $$I_{av+} = \frac{1}{2\pi} \int_{0}^{\pi} I_{pk} \sin(\theta) d\theta = \frac{I_{pk}}{2\pi} \left[-\cos\right]_0^\pi = \frac{I_{pk}}{\pi} .$$

Therefore, for a sine-wave \(I_{av+}=I_{pk}/\pi\). Since the average current limit of the PX200 is fixed at \(I_{av+}=0.7\), the maximum frequency sine-wave, or power bandwidth of the PX200, is equal to $$ f = \frac{0.7}{V_{pp} C}.$$

The above result is true for any periodic waveform such as triangular signals. In the 100V range, the power bandwidth is doubled. The RMS current for a sine-wave can also be related to the average current, $$ I_{av+} = \frac{\sqrt{2}}{\pi} I_{rms} .$$

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

Load Peak to Peak Voltage (200V Range)
Cap 200V 150V 100V 50V
10 nF 55 kHz 74 kHz 100 kHz 100 kHz
30 nF 55 kHz 74 kHz 100 kHz 100 kHz
100 nF 35 kHz 46 kHz 70 kHz 100 kHz
300 nF 11 kHz 15 kHz 23 kHz 46 kHz
1 uF 3.5 kHz 4.6 kHz 7.0 kHz 14 kHz
3 uF 1.1 kHz 1.5 kHz 2.3 kHz 4.6 kHz
10 uF 350 Hz 466 Hz 700 Hz 1.4 kHz
30 uF 116 Hz 155 Hz 233 Hz 466 Hz

Power Bandwidth versus
Load Capacitance (200V Range)

Load Peak to Peak Voltage (100V Range)
Cap 100V 75V 50V 25V
100 nF 100 kHz 100 kHz 100 kHz 100 kHz
300 nF 46 kHz 62 kHz 93 kHz 100 kHz
1 uF 14 kHz 18 kHz 28 kHz 56 kHz
3 uF 4.6 kHz 6.2 kHz 9.3 kHz 18 kHz
10 uF 1.4 kHz 1.8 kHz 2.8 kHz 5.6 kHz
30 uF 466 Hz 622 Hz 933 Hz 1.8 Hz

Power Bandwidth versus
Load Capacitance (100V Range)

In the above tables, the frequencies limited by slew-rate are marked in green while the frequencies limited by signal bandwidth are marked in blue. The slew-rate is approximately 35 V/uS which implies a maximum frequency of $$ f^{max} = \frac{35 \times 10^6}{\pi V_{pp}}.$$

In the following figures, the maximum frequency periodic signal in the 200V and 100V range is plotted against the peak-to-peak voltage.

px200 Power Bandwidth versus voltage and load capacitance

Power Bandwidth versus Voltage and Load capacitance
(200V Range)

px200 power bandwidth versus voltage and load capacitance

Power bandwidth versus Voltage and Load Capacitance
(100V Range)

Small Signal Bandwidth

px200 small signal frequency response

Small signal frequency response

Load Cap. Bandwidth
10 nF 393 kHz
30 nF 431 kHz
100 nF 367 kHz
300 nF 208 kHz
1 uF 88 kHz
3 uF 30 kHz
10 uF 9.3 kHz
30 uF 3.7 kHz
110 uF 1.3 kHz

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 that is inversely related to the load capacitance. Many manufacturers quote only the AC noise measured by a multimeter (20 Hz to 100 kHz) which is usually an underestimate.

The noise is measured with an SR560 low-noise amplifier (Gain = 1000), oscilloscope, and Agilent 34461A Voltmeter. The low-frequency noise is plotted below. The RMS value is 173 uV with a peak-to-peak voltage of 960 uV.

 

px200 low frequency noise from 0.03 hz to 20 hz

Low frequency noise from 0.03 Hz to 20 Hz. The RMS value is 173 uV, or 960 uVp-p

The high frequency noise 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 $$ \sigma = \sqrt{ \sigma_{LF}^2 + \sigma_{HF}^2 } .$$

Load Cap. Bandwidth HF Noise RMS Total Noise RMS
10 nF 393 kHz 379 uV 417 uV
30 nF 431 kHz 382 uV 419 uV
100 nF 367 kHz 382 uV 419 uV
300 nF 208 kHz 326 uV 369 uV
1 uF 88 kHz 234 uV 291 uV
3 uF 30 kHz 214 uV 275 uV
10 uF 9.3 kHz 198 uV 263 uV
30 uF 3.7 kHz 187 uV 255 uV
110 uF 1.3 kHz 183 uV 252 uV

RMS noise versus load capacitance
(0.03 Hz to 1 MHz)

Input and Offset Configuration

The input stage is a differential amplifier with an input impedance of 27k. The input signal ground is permitted to float by up to 0.6V before it is clamped to the system ground.

The input stage is normally non-inverting; however, it can be configured as inverting by changing LK9 and LK10 to their “B” positions. The default jumper position is “A” which is marked with a white bar on PCB overlay. The amplifier can be supplied with an inverting input by appending the order code with -INV.

Input Coniguration Code Link Positions
Non-inverting (default) LK9 and LK10 both “A”
Inverting -INV LK9 and LK10 both “B”

Input polarity configuration

The input offset source is also configurable. When LK21 is in the “A” position, the offset is derived from the on-board trim-pot R15, which is adjustable from zero to full-scale. The default configuration for LK21 is in “B” position where the offset voltage is derived from the front-panel potentiometer.

The standard offset voltage range is from zero volts to full-scale; however, for applications that require negative offset voltages, LK20 can be moved from the “A” to “B” position. In the “B” position, the offset range is from -100V to full-scale.

Offset Configuration Code Link Positions
0V to +200V Range (default) LK20 “A” Position
-100V to +200V Range -OR2 LK20 “B” Position
Front panel source (default) LK21 “B” Position
PCB trim-pot source -OS2 LK21 “A” Position

Offset voltage source configuration

Gain

The standard voltage gain is 20 V/V. However, in the 100 Volt range, a gain of 10 may be more convenient. This can be achieved by removing LK14 and LK15. In this configuration, the voltage monitor sensitivity becomes 1/10 V/V.

Bridged Mode

In bridged mode, two amplifiers are connected in series to double the output voltage range and power. To obtain +/-200V at the load, the amplifiers are configured as illustrated below. Both amplifiers are configured in the +/-100V range and the lower amplifier is also inverting. A +/-5V signal applied to both inputs will develop +/-200V at the output.

px200 bridge

Overload Protection

The Shutdown indicator will illuminate during a shutdown caused by a current overload or if the amplifier overheats as a result of excessive ambient temperature, poor air-flow, or fan failure. During shutdown, the amplifier output current is limited to a few mA and may float to the high or low voltage rail if the load impedance is high or capacitive.

When the amplifier is turned on, the overload protection circuit is engaged by default and will take approximately three seconds to reset

In addition to the internal shutdown triggers, the output stage of the amplifier can also be disabled by applying a positive voltage to the external shutdown connector (2V to +12V). The impedance of the external shutdown input is approximately 2.5k.

Enclosure

The PX200 Driver has a side air intake and rear exhaust. These vents should not be obstructed. If sufficient air-flow is not available, the amplifier will enter a thermal overload state as discussed in “Overload Protection”.

The PX200 amplifiers can be bolted together in a side-by-side two-channel arrangement. With the addition of rack-mount handles, this configuration can be mounted into a standard 19-inch rack. A 19-inch rack-mount kit is also available for a single amplifier.

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.

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