LeCroy DA1855A Operation - page 2
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.