Falco Systems WMA-IB-HS High Speed Phase Inverter Buffer

About this manual
This user manual is an integral part of the Falco Systems WMA-IB-HS phase inverter – buffer product. Please read it carefully and pay attention to the recommendations and instructions for safe use.

Operation of the phase inverter

The WMA-IB-HS is a low noise, high speed DC – 20MHz phase inverter – buffer designed to drive one or two high voltage amplifiers. It can be used:

• To drive two amplifiers in bridge mode by using both the buffered output and the inverting output, or
• As a high impedance buffer between a signal source and the amplifier
• The input of the WMA-IB-HS is switchable to 100kΩ input impedance and to 50Ω: The 50Ω setting is used with 50Ω sources such as function- or arbitrary waveform generators, to ensure waveform integrity even at high operating frequencies.
• The 100kΩ setting is used to buffer current limited signal sources such as typical computer controlled DAQ (data acquisition) cards.
• Internal gain switching circuitry makes sure that the output signal amplitude does not change with the setting of the switch when the input impedance switch is toggled (when driven from a 50Ω source).
• The outputs of the WMA-IB-HS can drive both high impedance and 50Ω high voltage amplifier inputs. The WMA-IB-HS can also be used as a high quality stand-alone phase inverter – buffer in a variety of other applications.
• The WMA-IB-HS ships with a customized Mean Well GS25B28-P1J power supply. The power supply connector, 315mAT fuse and on-off switch are on the rear panel of the WMA-IB-HS enclosure. A blue led indicates that the WMA-IB-HS is on. The outputs are on the left of the front panel to accommodate neat cabling to high voltage amplifiers that typically have their inputs at the left side too.

Bridge mode
The WMA-IB-HS can be used to double the maximum output voltage driving a load, such as a piezo actuator, EO (electro-optical) modulator, or MEMS (electromechanical systems) device, among many others. This is achieved by driving two high voltage amplifiers both with the same signal, but with opposite polarity. The outputs of the amplifiers are connected in bridge mode. Fig. 1 shows the concept of the bridge mode circuit.

The WMA-IB-HS inverts the signal and provides the signal for both amplifiers. The outputs of the two amplifiers are connected to the floating, ungrounded load. The WMA-IB-HS phase inverter – buffer amplifies 1x. If both amplifiers amplify e.g. 20x, the total output voltage across the load will be doubled in bridge mode, i.e. 40x in this case. Fig. 2 shows an actual setup with the high-speed phase inverter buffer connected to two high voltage amplifiers to drive them in bridge mode.
When two amplifiers are driven in bridge mode, the high voltage output signal with twice the amplitude of the individual high voltage amplifiers is available between the inner pins of the two high voltage amplifier BNC outputs and can be connected to the load (Fig 3). Make sure that the load is not grounded to the same ground as the amplifiers, as this would short-circuit one of the two high voltage amplifiers. This will not damage the amplifier (if it is short-circuit proof) but would reduce the output voltage available to that of a single amplifier only. The high speed phase inverter – buffer in combination with two Falco Systems high voltage amplifiers is capable of both very high speed and low noise performance. This performance can only be obtained with correct shielding of the cables connecting to the load and, if possible, shielding of the load itself. Solid BNC connectors and/or short, high quality BNC cables are recommended.
Some loads, such as certain EO-modulators, have a differential connector available, or two individual connectors, to drive them differentially (Fig. 4). The housing of the modulator is connected to the shield of the cables this way, resulting in good interference rejection.
This scheme is also the recommended one if the user has the possibility to design the connections of the load him/herself. In situations where driving the load differentially with two connectors is impossible, e.g. because the load has only a single connector, both amplifier outputs have to be connected together at the load, as depicted in Fig. 5.

• If one of the two connections of the connector is connected to the (conductive) housing of the load, check that:
  the housing/outside of the load floats with respect to the ground of the amplifiers, i.e. it makes no contact with the electrical circuit to which the amplifiers belong, other than via the output cables, and
• the housing/outside of the load and the BNC connector itself cannot be touched, as it carries the full output voltage of one of the high voltage amplifiers. For this reason the sign is present on the enclosure. The use of an insulated BNC connector is recommended. To aid in connecting floating loads in bridge mode, Falco Systems offers a special ‘bridge mode insulated tee-cable’ (Fig. 6). This cable takes the two amplifier cables on BNC connectors, and has a third BNC connector, where the inner conductor of one input cable is connected to the inner pin, and the inner conductor of the other cable to the outer ring, which is normally associated with the OV shield. This functionality is very different from a normal BNC tee-adapter, which is only used to connect the inner conductor of a BNC cable to two cables, with all inner pins connected together.

website www.falco-systems.com

Required amplifier properties

The WMA-IB-HS phase inverter – buffer can be used with many high voltage amplifiers, and is not limited to driving amplifiers of the Falco Systems brand. Most amplifiers with an output current limiter are suitable, as the current limiter will ensure that the maximum power dissipation inside the amplifier will not be exceeded. When the setup is used with fast changing signals, the voltage and current transients at the amplifier outputs may be slightly different in bridge mode than when the load is grounded. For most amplifiers this will be no problem, but when in doubt, please contact the manufacturer of the high voltage amplifiers before using the amplifiers in bridge mode.Amplifiers without a current limiter will dissipate twice the normal power. The double voltage will be shared equally between the amplifiers in bridge mode, but the doubled voltage across the load will result in a doubled current, which flows through both amplifiers. Depending on the details of the setup, this higher dissipation may or may not be a problem. Again, when in doubt, please contact the manufacturer of the amplifiers before using the amplifiers in bridge mode.

Buffer mode

Although primarily intended for driving high voltage amplifiers in bridge mode, the WMA-IB-HS can also be used as a stand- alone buffer to connect low power signal sources to equipment with a 500 input impedance. Please note that computer- controlled setups with DAQ (data acquisition) cards often are not able to drive a 500 high voltage amplifier input directly. This is caused by the very limited current capability of the outputs of typical DAQ cards, which is insufficient to drive a 500 input. An example is driving the input of a Falco Systems WMA-300 high-speed high voltage amplifier from a DAQ card. This will result in a highly distorted and clipped signal coming out of the DAQ card at higher output voltages. The solution is to use a WMA-IB-HS as the buffer between the low current signal source and the 500 equipment (Fig. 7).The input of the WMA-IB-HS is set to the high impedance 100kQ setting not to load the signal source unduly, and its ‘buffered out will drive 50Q equipment without any problems. If the signal coming from the source is fast-changing, such as a square wave or high frequency sine wave, then mount the WMA-IB-HS very close to the signal source. This is done to prevent reflections in the non-500 connection between the signal source and the WIMA- IB-HS buffer input.

50Q: preserving signal amplitude
The WMA-IB-HS is equipped with both a 500 and a 100kQ input. A typical 500 source such as a function or arbitrary waveform generator has a 500 output and will form a 1:2 voltage divider with the 500 input resistance of the WMA-IB-HS. To prevent the loss in signal amplitude due to this voltage divider, the WMA-IB-HS amplifies the signal at its input by a factor 2 when the input is switched to the 500 setting. The factor 2 ensures that the signal at the output has the same amplitude when driven from a 500 source, irrespective of whether the input is set to 500 or 100ke. If the signal source has a very low output resistance and drives the 500 input, the voltage gain is 2x, because the 1:2 voltage divider is absent. When the WMA-IB-HS drives a high impedance load such as an amplifier input, the voltage at the output will be the same as the voltage at the input. If the output drives a 500 input, the voltage divider consisting of the 500 output resistance of the WMA-IB-HS and the 500 input of the amplifier will divide the signal available at the high voltage amplifier input by a factor 2. This is just what a 500 signal source such as a function generator would do. Fig. 8 illustrates the gain of the WMA- B-HS for different situations

More information about 500 systems can be found online in the Falco Systems application note “High voltage amplifiers and the ubiquitous 50 Ohm: caveats and benefits” at: www.falco-systems.com/applications.html

Recommendations and safety
Recommendations:  Heed the advice in the ‘connecting the load’ section of the manual. In short: do not short circuit one of the amplifiers by grounding the load, and make sure the voltage-carrying parts of the load cannot be touched during operation.

• Never apply more than +10V (or less than -10V) to the phase inverter/buffer input to prevent damage.
• The phase inverter/buffer cannot be damaged by a short-circuit condition or capacitive loading, but avoid:
• Connecting a charged capacitor to the input or output.
• Connecting a highly inductive load to the output (such as a coil).
• Do not connect anything to the phase inverter – buffer that can act as an antenna.
• This product should only be cleaned with a soft, slightly moist cloth. Disconnect the phase inverter/buffer from the power supply and all equipment before cleaning.

Safety

• The WMA-IB-HS high speed phase inverter – buffer is only suitable for indoor use in a class II environment (domestic, light industrial).
• Only use the power supply adapter supplied by Falco Systems: Mean Well GS25B28-P1J, 100-240V~ 50/60Hz in, 28V 25W DC out, with custom MiniDIN connector.
• Only replace fuses with the correct type: 5x20mm 315mAT 230V fuse on the rear panel.
• This product cannot be powered by nonsinusoidal mains power generators.
• Only replace a damaged power cord with an equivalent type: H03VVH2-F 2X 0,75 mm2, with Euro to C7 equipment connector.
• The airflow to and from the WMA-IB-HS should not be blocked or impeded, to allow for adequate ventilation.

Transmitter mode
This high speed phase inverter – buffer can generate a significant amount of power at frequencies used for radio transmission and reception. It should not be used for telecommunication as described in the
R&TTE directive 95/5/EC. Always use coaxial cables.

WMA-IB-HS phase inverter – buffer characteristics

Technical specifications

Harmonized standards
This product complies with the following standards:
Safety: EN61010-1
EMC: EN61326
FCC: 47 CFR 15

The mark is present on the WMA-IBHS to indicate compliance of this equipment with the European Union safety and EMC regulations, while   FC the mark has been added to indicate compliance with the United States FCC regulations.

WEEE and RoHS
Do not dispose of the WMA-IB-HS phase inverter – buffer as standard waste, but bring it to a WEEE electronic waste collection point. This is indicated by the sign on the WMA-IB-HS. The WMA- IB-HS has been built in compliance with the RoHS directive.

Warranty

Falco Systems products are guaranteed against malfunction due to defects in materials or workmanship for a period of 1 year from the date of shipment. If a malfunction occurs during this period, the product will be repaired or replaced without charge. The product will be returned to the customer prepaid. The warranty does not apply to:

• Exterior finish or appearance
• Malfunction resulting from use or operation of the product in other ways than specified in the user manual
• Malfunctioning due to misuse or abuse of the product
• Malfunctioning occurring after changes or repairs have been made by anyone other than Falco Systems. To obtain warranty service, the customer has to inform Falco Systems first via info@falco-systems.com to receive further instructions.
• To obtain warranty service, the customer has to inform Falco Systems first via info@falco-systems.com to receive further instructions.
• Falco Systems will not be liable for any consequential damages, including, without limitation, devices or equipment connected to the product, injury to persons or property or loss of use. See for more details the Falco Systems Standard Terms and Conditions of Sale, which can also be obtained via info@falco-systems.com

User manual version

• User manual version: 1.6
• Date: October 25, 2024
• Falco Systems
• Falco Systems
• Vaartweg 204
• 1217SZ Hilversum
• The Netherlands
• Phone +31 (0)6 21840996
• Email info@falco-systems.com
• Website www.falco-systems.com

FAQ

• How do I switch between the input impedance settings?
  To switch between the 50 and 100k input impedance settings, use the switch provided on the WMA-IB-HS device.
• Can the WMA-IB-HS be used with any power supply?
  No, the WMA-IB-HS comes with a customized Mean Well GS25B28-P1J power supply which is recommended for optimal performance.

Documents / Resources

Falco Systems WMA-IB-HS High Speed Phase Inverter Buffer [pdf] User Manual WMA-IB-HS, WMA-IB-HS High Speed Phase Inverter Buffer, High Speed Phase Inverter Buffer, Phase Inverter Buffer, Inverter Buffer, Buffer

References

• User Manual