15.2.1
Passive, single
-
ended voltage probes
Voltage probes divide a single
-
ended input signal by a specific factor.
10 * Uin
Uin
Passive Probe
(+)
GND
GND
Single-ended amplifier
9M
900K
100K
(+)
(+)
(-)
Figure 15.7:
Typical example of a voltage probe
Theoretically, voltage probes are simply passive in
-
line resistors in series with
the positive input of a single
-
ended amplifier. Together with the input resistor
of the amplifier, they form a voltage divider so that the voltage in series with the
amplifier itself is divided. As there is also a capacitive component in this divider,
the input capacitance of the amplifier and the so
-
called “compensation range”
of the probe need to match. Otherwise, signal distortion might occur.
By selecting a higher resistance probe, the divider ratio increases so that large
input ranges can be achieved. Voltage probes do not provide or add either
isolation or common mode voltage rejection. These probes can only be used
in series with single
-
ended amplifiers.
Voltage probes typically decrease the overall accuracy of the system (caused
by the inaccuracy of the input divider ratio formed by the external probe
resistance and the internal amplifier resistance).
GEN3i
I3763-3.1 en HBM: public
347
