Falco Systems WMA-100 User Manual - Falco Systems
Falco Systems WMA-100 • High V
oltage
Amplifier DC - 500kHz
Falco Systems
WMA-100, High Voltage Amplifier DC - 500kHz
8
The load
The output impedance of the WMA-100 model is 50Ω, to ensure stability with all
capacitive loads. The amplifier 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 reflections (an effect related to the finite speed of light), and current
limiting due to the cable capacitance. Although the amplifier itself remains fully
stable, using less than 5 meter of output cable is recommended for
the WMA-100 amplifier to obtain optimal results.
Transmitter mode
This amplifier can generate a significant amount of power at frequencies used
for radio transmission and reception. The amplifier should not be used for
telecommunication as described in the R&TTE directive 95/5/EC. Also for this
reason always use coaxial cables.
Amplifier characteristics
In the following pages, several amplifier 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)