Reference
80E00 ElectricalSampling Modules User Manual 19
propagation time fromthe acquisition point to the short in the device under test
and back. See Figure 8.
250mV
0V
EiEr
Figure8: Stepgenerator witha shorted output
OperationInto a 50 ΩLoad. Initially, the diode switch is conducting --10 mA.
Since the step-generatoroutput is connected to a 50 Ωload, the resistance to
ground at the acquisitionpoint is 25 Ω(becaus e of the internal 50 Ωimpedance).
+250mV
0V
Ei
Er
Figure9: Stepgeneration with a 50 Ωload
When the diodeswitch opens (reverse-biased), apparent resistance to ground at
the acquisition point (andat the channel connector) is 25 Ωbecause the internal
termination resistanceis 50 Ωin parallel with the connector impedance of 50 Ω.
The voltage atthe acquisition point rises to +250 mV.
The transition propagatesto the 50 Ωload and no reflect ion occurs.
OperationInto an Open. Initially, the diode switch is conducting --10mA. Since
the step-generatoroutput is open, the resistance to ground at the acquisition point
is 50 Ω(because of the internal 50 Ωimpedance).
+250mV
0V
+500mV
Ei
Er
Figure10: Stepgeneration with an open circuit