DA1855A Differential Amplifier
3-2
ISSUED: July 2002
DA1855A-OM-E Rev A
FRONT PANEL
Input Connectors
Signals applied to the
+INPUT
and the –
INPUT
are connected
either directly to the DA1855A amplifier’s inputs or to the input
attenuators. Maximum input voltage is ±200 Vp
A signal connected to the
+INPUT
will remain its polarity at the
output connector. A signal connected to the –
INPUT
will be
inverted in polarity.
Attenuators
The input attenuators are passive networks which divide each
signal by ten.
In
÷÷
1
mode the front panel input connectors are directly
connected to the DA1855A amplifier's differential inputs.
In
÷÷
10
mode each front panel input connector is connected to a
passive 1 M
Ω
attenuator. The attenuator output is connected to
the DA1855A amplifier's corresponding differential input. The
signal at each input is attenuated by a factor of ten.
Gain
The DA1855A amplifier gain (amplification) is selectable between
X1
and
X10
. The amplified signal appears at the rear panel
AMPLIFIER OUTPUT
connector.
Gain will affect the differential mode output signal by amplifying
the signal difference between the
+INPUT
and the –
INPUT
, but
will not affect the common mode signal, the signal common to the
+INPUT
and them –
INPUT
.
Output Termination
Proper gain is obtained when the DA1855A drives a 50
Ω
load
such as an oscilloscope with input impedance set to 50
Ω
.
Automatic 50
Ω
termination is obtained when the DA1855A is
connected to a LeCroy oscilloscope through the ProBus
interface.
An instrument with only a 1 M
Ω
input impedance available should
have a 50
Ω
coaxial termination placed on its input connector.
The DA1855A is then connected to the oscilloscope through the
coaxial termination.
