Falco Systems WMA-100
High Voltage Amplier DC - 500kHz
USER
manual
Falco Systems WMA-100 • High Voltage Amplier DC - 500kHz
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Falco Systems WMA-100, High Voltage Amplier DC - 500kHz
• High voltage: 20x amplification up to +175V and -175V output voltage with respect
to ground
• DC to 500kHz at (-3dB) large signal bandwidth and 100mA output current
• Very low noise: ~350μVrms, and even lower when capacitive loads are driven
• No overshoot with capacitive loads: bandwidth changes automatically to
ensure stability
• Short-circuit protected output
• Adjustable DC offset
About this manual
This user manual is an integral part of the Falco Systems WMA-100 high voltage
amplier product. Please read it carefully and pay attention to the recommenda-
tions and instructions for safe use.
The WMA-100 high voltage amplier: getting started
The Falco Systems WMA-100 model is a high quality, cost-effective, high voltage,
linear laboratory amplier. Its wide bandwidth and large voltage range make it an
excellent choice for use with MEMS devices, EO-modulators, piezo positioning
systems, beam steering, ultrasonics, dielectric studies, and many other
applications. It is designed to be fully stable and free of spurious signals with
any capacitive load.
The amplication is 20x (xed). The amplier has a range of –175V to +175V, a
large signal bandwidth of 500kHz @ -3dB, a typical slew rate of 350V/μs, and
a noise level of ~350μVrms. The short-circuit protection with a fast current limit
of ±100mA make this amplier suitable for both normal daily laboratory use and
automated measurement systems.
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!
Recommendations:
• Never apply more than +15V (-15V) to the amplier input to prevent damage.
• A short voltage spike may appear at the output, when the amplier is turned on or off.
Pay attention not to damage sensitive circuitry or equipment already connected.
• The amplier cannot be damaged by a short-circuit condition or capacitive loading,
but two situations should be avoided:
- 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 output that can act as an antenna.
• This product should only be cleaned with a soft, slightly moist cloth. Unplug the
WMA-100 amplier from the mains power before cleaning.
Safety
• This product is able to produce over 175V at more than 100mA at its output, which is a
very high level (risk of electric shock). Safety measures should be taken accordingly.
This is indicated by the sign above the output connector of the amplier.
• This product is a Class I appliance which requires a mains connection with protective
earth.
• Always position the WMA-100 amplier such that the on/off power switch is easily
accessible.
• The airow to and from the WMA-100 amplier should not be blocked or impeded, both
at the front and the back side.
• The internal circuitry of the amplier operates at high voltage. Only qualied personnel
from Falco Systems should service this amplier.
• Only replace fuses with the correct type:
- 230V version of the WMA-100: 250V 250mA 5x20mm slow blow.
- 115V version of the WMA-100: 250V 500mA 5x20mm slow blow.
• The Falco Systems WMA-100 amplier is only suitable for indoor use in a class II
environment (domestic, light industrial).
• Non-sinusoidal mains power generators cannot be used to power this product.
Falco Systems WMA-100, High Voltage Amplier DC - 500kHz
Falco Systems WMA-100 • High Voltage Amplier DC - 500kHz
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Detailed properties of the WMA-100 high voltage amplier
Input
The input impedance of the WMA-100 high voltage amplier is a 100kΩ resistor
to ground, in parallel with 68pF to prevent electrostatic discharge (ESD) input
damage. This resistor adds some noise to the output voltage unless a low-impe-
dance source (e.g. a 50Ω output function generator) is connected to the input.
The noise will be slightly higher when the amplier input is left open.
The 100kΩ resistor also adds to the output offset voltage because the offset
current of the input amplier generates a voltage over this resistor. This output
offset voltage is ~10mV if the input is left open. When the input is shorted or
connected to a low-impedance source, the offset is reduced to ~8mV.
A high-speed amplier like the WMA-100 model can never be made fully
insensitive to input overload conditions, as this would limit the performance of
the amplier signicantly. For normal operation, input voltages should remain
in the –8.75V to +8.75V range, resulting, with an amplication of 20x, in an
output voltage swing of –175V to +175V. Below -15V and above +15V, the input
protection circuitry will limit the voltage fed to the amplier, but the amplier may
be permanently damaged if the current of the source is not limited.
Output
The WMA-100 model has been designed to be fully stable with all capacitive
loads. It has been optimized for a perfect step-response, but it is also a very
good linear and sine-wave amplier.
The WMA-100 amplier has a clever feedback system, which ensures that
no signicant overshoot occurs at any capacitive load. The bandwidth of the
amplier is automatically reduced to ensure stability. Instability under capacitive
loading conditions is a common
problem of other high-speed negative feedback ampliers, often resulting in
unwanted output overshoot voltages, and, in extreme cases, oscillations.
Short-circuiting this amplier will not break down the amplier, due to the extre-
mely fast current limiting circuit that has been employed.
If output monitoring is required, it is recommended to connect a 10x oscil-
loscope probe to the output. A special BNC to probe tip connector is usually
supplied with the probe (Fig. 1). However, the user can choose a different way
of connecting the oscilloscope, as long as care is taken with the high output vol-
tage. Using non-coaxial cable can cause overshoot in the oscilloscope reading.
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Falco Systems WMA-100, High Voltage Amplier DC - 500kHz
Figure 1. A 10x probe connected for monitoring the output signal
Noise
The noise of the amplier (~350μVrms) is lowest when a low-impedance source
is used, such as a pre-amplier output or a 50Ω function generator output. An
easy way to assess the noise performance of the amplier without picking up
interference is to connect a 50Ω coaxial load resistor to the input (Fig. 2) and
monitoring noise voltage at the output with a sensitive amplier.
The output noise will be lower when the bandwidth of the amplier is reduced,
which happens when a signicant capacitive load is connected to the output
(see Fig. 16 for a detailed measured curve).
Figure 2. If assessment of the amplier noise is necessary, connect e.g. a 50Ω
coaxial load resistor to the input to provide a low-impedance input connection.
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Offset adjustment
The WMA-100 model provides an offset control knob to enable the amplier to
generate offset voltages over the full output range (Fig. 3). The offset control
can be switched to ‘Off’ with a small rocker switch on the front panel to obtain
the lowest noise and highest DC stability of the amplier. Turning the offset
control to ‘On’ enables the DC control knob.
The DC offset voltage reacts to adjustments of this knob in a second. With the
offset control turned to ‘On’, the noise performance of the amplier becomes
slightly higher: ~600μVrms instead of ~350μVrms.
Figure 3. Offset circuitry ‘On-Off’ switch and offset control knob
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The load
The output impedance of the WMA-100 model is 50Ω, to ensure stability with all
capacitive loads. The amplier is generally used for high-impedance ap-
plications where the load is capacitive. This is the case for MEMS devices,
EO-modulators and piezo’s alike. It should be noted that a coaxial cable itself
also presents a capacitive load of approximately 100pF/m. The cable that is
connected may limit the maximum usable current at high frequencies.
Matched loading with a 50Ω load circuit is possible by connecting a 50Ω resistor
in series with the output to ground, but is not recommended. The advantage is
that excessively long cables will not distort the waveforms. The disadvantage
is a highly reduced voltage range (100mA in 50Ω gives 5V maximum instead of
175V maximum).With sensitive and/or high-frequency measurements, coaxial
cables should be used for connecting both the input and the output, and its
length should be minimized. Otherwise the cables will cause overshoot due
to cable reections (an effect related to the nite speed of light), and current
limiting due to the cable capacitance. Although the amplier itself remains fully
stable, using less than 5 meter of output cable is recommended for
the WMA-100 amplier to obtain optimal results.
Transmitter mode
This amplier can generate a signicant amount of power at frequencies used
for radio transmission and reception. The amplier should not be used for
telecommunication as described in the R&TTE directive 95/5/EC. Also for this
reason always use coaxial cables.
Amplier characteristics
In the following pages, several amplier characteristics are illustrated:
• Frequency response as a function of capacitive load (Fig. 4, 5)
• Sine and triangle wave responses (Fig. 6, 7)
• Square wave response (Fig. 8, 9, 10)
• Step response (Fig. 11)
• Capacitive load dependency of square wave output (Fig. 12)
• Noise and offset with and without offset control engaged (Fig. 13, 14)
• Noise spectrum (Fig. 15)
• Rms output noise voltage versus capacitive load (Fig. 16)
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Figure 4. Frequency response at 300Vpp output voltage with different
capacitive loads
Figure 5. Frequency response at 1Vpp output voltage with different capacitive
loads
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Figure 6. Sine wave 300Vpp 1kHz
Figure 7. Triangle wave 300Vpp 1kHz
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Figure 8. Square wave 300Vpp 1kHz
Figure 9. Square wave 300Vpp 100kHz
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Figure 10. Square wave 1Vpp 100kHz (small signal response)
Figure 11a. 300Vpp step response 10-90%: up in 1.0μs
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Falco Systems WMA-100 • High Voltage Amplier DC - 500kHz
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Figure 11b. 300Vpp step response 10-90%: down in 0.9μs
Figure 11c. 0 to 150V step response 10-90%: up in 0.8μs
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Figure 11d. 150 - 0V step response 10-90%: down in 0.8μs
Figure 12a. 0pF load
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Figure 12b. 100pF load
Figure 12c. 1nF load
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Figure 12d. 10nF load
Figure 12e. 100nF load
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Figure 12f. 1μF load
Figure 12g. 10μF load
Figure 12. 300Vpp square wave response under different capacitive loading
conditions. The 100mA current limit limits the speed at which the capacitor can
be charged.The bandwidth adjustments of the amplier with different capacitive
loads preventing overshoot are clearly visible. Note the difference of the hori-
zontal timescale in the gures.
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Figure 13. Noise (~350μVrms measured with a true rms voltmeter) and typical
offset with the offset control switched to ‘Off’. The noise and offset may appear
to be higher than shown here if the amplier input is not connected to a low-
impedance source.
Figure 14. Noise (~600μVrms measured with a true rms voltmeter) with the
offset control switched to ‘On’. In addition, the short term drift of the offset is
around 5mV.
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Figure 15. Noise spectrum (262144 bins 15MHz FFT) with offset control swit-
ched to ‘Off’.
Figure 16. Rms output noise voltage versus capacitive load with offset control
switched to ‘Off’.
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Technical specications
Amplication : 20x, xed
Bandwidth : DC - 500kHz @ -3dB large signal bandwidth
Slew rate : 350V/μs typical
Output voltage : -175V to +175V
Current : 100mA typical with limiter
Noise and offset : 350μVrms output noise typical, 8mV offset typical
Input impedance : 100kΩ
Output impedance : 50Ω
Stability : stable with all capacitive and resistive loads, no
overshoot > 5%
Power : 230V 50Hz AC, 50W or 115V 60 Hz AC, 50W
Mains fuse : 2x 0.25A 250V slow blow (230V version) or 2x 0.5A
250V slow blow (115V version)
Safety : Class I - requires mains power connector with
protective earth
Overvoltage : Category II
Operating temperature : 15 - 30°C
Storage temperature : 0 - 60°C
Relative humidity : 30 - 70% non-condensing
Maximum usage height : 2000m
Dimensions : 52 x 165 x 220 mm
Weight : 2.5 kg
Country of origin : The Netherlands
Specications may be subject to change
Harmonized standards
This product complies with the following harmonized European
standards:
Safety : EN61010-1
EMC : EN61326
WEEE and RoHS
Do not dispose of the WMA-100 amplier as standard waste, but bring it
to a WEEE electronic waste collection point. The amplier has been built
in compliance with the RoHS directive.
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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 nish or appearance
• Malfunction resulting from use or operation of the product in other ways than
specied 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 rst
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.
Falco Systems WMA-100 • High Voltage Amplier DC - 500kHz
Falco Systems WMA-100, High Voltage Amplier DC - 500kHz
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User manual version 2.1 March 2016
www.falco-systems.com
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