Falco Systems WMA-280 User manual

USER MANUAL
-150V to +150V output
300µVrms output noise
2mV output offset voltage
±300mA Output current limit
DC to 100kHz at -3dB full
power bandwidth
Short-circuit protected output
For precise positioning of
MEMS devices, for EO-modulators,
driver for PZT (piezo) positioning,
beam steering, ultrasonics, …
About this manual
This user manual is an integral part of the Falco Systems
WMA-280 amplifier product. Please read it carefully and
pay attention to the recommendations and the instructions
for safe use.
General description
The Falco Systems WMA-280 is an ultra-low noise, high-
voltage linear laboratory amplifier for demanding
applications. Its extreme voltage precision (2mV output
offset voltage), ultra-low output noise (300µVrms) and large
voltage range (-150 to +150V) make it an excellent choice
for measurements where high precision is important. The
bandwidth is DC - 100kHz. It can be used for precise
positioning of MEMS devices (micromachines), with EO-
modulators, PZT (piezo) driver positioning systems, beam
steering components, ultrasonics, and many more.
Through the extensive use of computer modelling and
state-of-the-art design concepts, this amplifier can be used
in many applications, including those where conventional
amplifiers are difficult to apply. It is designed to be
absolutely stable and free of spurious signals with any
capacitive load.
The amplification is 20x ±0.1% (fixed). A fast current limit
of ±300mA (typical) and a fast short-circuit protection
make this amplifier suitable for both the normal daily
laboratory use (and abuse), and automated measurement
systems.
Safety
- This product is able to produce over 150V at more than
300mA at its output, which is a dangerously high
level (risk of electric shock). Safety measures
should be taken accordingly.
- Only use this appliance with a mains connection with
protective earth
- The internal circuitry of the amplifier operates at high
voltage. Only qualified personnel from Falco Systems
should service this amplifier.
- When the amplifier is turned on or off, a short voltage
spike may appear at the output which may damage
circuitry already connected to it.
- Replace fuses with 250V 630mA 5x20mm slow blow
rated fuses only.
- The Falco Systems WMA-280 is only suitable for indoor
use in a class II environment (domestic, light industrial).
- This product should only be cleaned with a soft, slightly
moist cloth. Unplug the WMA-280 from the mains power
before cleaning.
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The inputs: connectors, noise and offset
The WMA-280 has been equipped with both a standard
BNC input connector and a differential Thomas & Betts
multi-pole connector. The latter is to be used when lowest
noise and interference performance is required (see
below). The amplifier comes with a spare contra-connector
for easy interfacing to other equipment. When using the
differential connector (with a differential signal), keep in
mind that the WMA-280 output ground and housing are
internally connected to the mains earth for safety.
Both inputs of the WMA-280 are grounded with 1kΩ, 0.1%
resistors, in parallel with 100pF to prevent ESD
(electrostatic discharge) input damage. These resistors
add some noise to the output voltage unless they are
bypassed by using a low-impedance source connected to
the inputs. With a finite-resistance source (e.g. 50Ω), the
input resistance also forms a resistive voltage divider,
which may influence the exact 20.0x amplification factor.
This deviation is well-known from the voltage divider
equation however, and can be easily compensated for in
the input signal if required. When the BNC connector is
used, the negative input of the differential input amplifier is
unused and sees the internal 1kΩas a small noise source.
The 1kΩresistors also add to the offset voltage because
the input offset current of the input amplifiers generates a
voltage over these resistors. This output offset voltage
may become as large as 3mV if both inputs are
unconnected. By using the differential inputs or grounding
the unused input on the differential connector when using
the BNC connector, the offset is reduced to less than 2mV.
Input protection
An ultra-low noise amplifier like the WMA-280 can never
be made fully insensitive to input overload conditions, as
this would limit the noise performance of the amplifier to
an unacceptably low level. Resistors in the input lines limit
the input current to a safe value as long as the input
voltage is not above ±15V.
For normal operation, input voltages should remain in the
–7.5V to +7.5V range, resulting with an amplification of
20x in an output voltage swing of –150V to +150V.
Above 15V (-15V) at the input, the amplifier may be
permanently damaged if the current of the source is not
limited.
Never apply more than +15V (-15V) to the amplifier input!
Output protection
The WMA-280 has been designed to be fully stable with all
capacitive loads. Instability under capacitive loading
conditions is a common problem of high-speed negative
feedback amplifiers on the market, often resulting in
unwanted overshoot voltages, and, in extreme cases,
oscillations (check the respective manuals and datasheets
for details). In the WMA-280, this problem has been solved
by a clever feedback system. Although overshoot may
occur at certain capacitive loads the amplifier will never
oscillate.
Overloading or short-circuiting this amplifier will not break
down the amplifier, due to the extremely fast current
limiting circuit that has been employed.
Although the amplifier cannot be damaged by a short-
circuit condition or capacitive loading, two situations
should be avoided:
-Connecting a charged capacitor
-Using high inductance values (coils)
The load
The output impedance of the WMA-280 is in the milliohms
range. The amplifier is generally used for high-impedance
applications where the load is mainly capacitive. This is
true for MEMS devices, EO-modulators and PZT's
(piezo’s) alike. Resistive loads can be used as well. The
amplifier behaves neatly with capacitances up to 10nF, but
may show significant offset voltages if the capacitive load
is higher and high frequency signals are amplified.
If output monitoring is required, it is recommended to
connect a 10x oscilloscope 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 voltage. Pieces of non-coaxial
cable in the connection can cause overshoot in the
oscilloscope reading.
The amplifier should not be used for telecommunication as
described in the R&TTE directive 95/5/EC.
Figure 1. The 10x probe connected for monitoring the
output signal

Amplifier characteristics
In the following pages, several amplifier characteristics are
shown:
-Frequency response (Fig. 2, 3)
-Noise and offset (Figure 4)
-Integrated output noise spectrum (Figure 5)
-Square wave response (Fig. 6, 7)
-Slew rate (Fig. 8)
-Triangle and sine response (Fig. 9, 10)
-Capacitive load dependency of square wave
output (Fig. 11)
300
250
200
150
100
50
0
101102103104105106
Frequency (Hz)
Output amplitude (Volt)
Figure 2. Frequency response at 300Vpp output voltage
Frequency (Hz)
Output amplitude (Volt)
3.0
2.5
2.0
1.5
1.0
0.5
0.0
101102103104105106
Figure 3. Frequency response at 3Vpp output voltage
Figure 4. Noise and offset
Frequency (Hz)
Integrated noise (mV rms)
0.28
0.26
0.24
0.22
0.20
0.18
0.16
0.14
0.12
102103104105106
Figure 5. Integrated output noise spectrum
Figure 6. 240Vpp 10kHz square wave

Figure 7. 30mVpp small signal 10kHz square wave
300Vpp step up in 4.09µs 300Vpp step down in 3.68µs
0V to 150V in 4.19µs 150V to 0V in 2.83µs
Figure 8. Slew rate (definition: step response from 10% to
90% signal). 240V in 4µs ≈60V/µs
Figure 9. Triangle wave 300Vpp 1kHz
Figure 10. Sine wave 300Vpp 1kHz
0pF 150pF
1.5nF 4.7nF
Figure 11. 10kHz square wave response with different
capacitive loading conditions. The 300mA current limit
limits the speed at which the capacitor can be charged and
some overshoot occurs with large capacitors.
Technical specifications
Amplification: 20x 0.1%, fixed
Bandwidth: DC – 100kHz @ -3dB
Output voltage: -150V to +150V
Current: 300mA typical with limiter
Output noise: 300µVrms typical
Output offset voltage: 2mV typical
Maximum input voltage: ±15V
Input impedance: 1kΩ 0.1% // 100pF

Output impedance: ±0.1Ω
Stability: stable with all capacitive and resistive
loads
Power: 230V 50Hz AC, 120W
Mains fuse: 2x 0.63A 230V slow blow
Class 1 safety product: requires mains power
supply connector with earth
Do not use: non-sinusoidal power generators,
indoor use only
Operating temperature: 15 – 30°C
Storage temperature: 0 – 50°C
Relative humidity: 30 – 70% non-condensing
Dimensions: 280 x 280 x 160 mm
Weight: 6,8kg
Warranty: 1 year
Country of origin: The Netherlands
Specifications are subject to change
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 such a malfunction occurs during this period, the product
will be repaired or replaced (at our option) 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 other than as specified in the user manual
-Malfunctioning due to misuse or abuse of the product
-Malfunctioning occurring any time after changes or
repairs have been made to the product by anyone
other than Falco Systems.
To obtain warranty service, the customer must inform
Falco Systems first, and then send the product, prepaid, to
Falco Systems together with a proof of purchase of the
product in the form of a bill of sale or receipted invoice.
This warranty explicitly only covers the product itself. The
repair or replacement including return to the customer are
the only services provided to the customer in this respect.
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.
User manual version
User manual version: 1.0
Date: October 4, 2008
Harmonized standards
This product complies with the following harmonized
European standards:
Safety: EN61010-1
EMC: EN61326
WEEE
Do not dispose of the WMA-280 as standard waste, but
bring it to a WEEE electronic waste collection point.
Falco Systems
Falco Systems
Gelderlandplein 75 L
1082 LV Amsterdam
The Netherlands
Tel. [phone]
Fax. [phone]
Email: [email protected]
http://www.falco-systems.com