Manual

DA1855A Differential Amplifier
28 922258-00 Rev A
the centerline. Following are a few observations on using the DA1855A comparison voltage mode
(V
COMP
):
• The negative input and its AC, OFF and DC coupling are disabled. Instead of being a
differential amplifier, the DA1855A becomes a differential comparator. It compares the
voltage present at the +INPUT with the output of the Precision Voltage Generator and when
they are equal, the output of the DA1855A is zero volts.
• The value displayed by the Precision Voltage Generator indicates a waveform’s voltage, with
respect to ground, as it passes through the oscilloscope display’s centerline. By using the
DA1855A in the comparison voltage mode and the oscilloscope in a high sensitivity setting,
highly accurate voltage measurements can be made.
Differential Offset Operation (VDIFF)
Set the DA1855A up as follows through the oscilloscope user interface:
PVG Mode
V
COMP
+Coupling
DC
DA1855A (Atten/Gain)
Manual
List Select: Upper BWL
FULL BWL
List Select: Gain
X10
List Select: Atten
÷1
List Select Input R
1 M Ω
Leaving the OFFSET control set as in the previous example, the DA1855A front panel indicators
should be lit as follows:
+INPUT
DC
–INPUT
V
COMP
BW LIMIT
FULL
GAIN
X10
ATTENUATOR ÷
÷1
INPUT RESISTANCE
1 M Ω
PVG
+0.0500
COMPARISON or
DIFFERENTIAL
COMPARISON
EFFECTIVE GAIN
X10