DA1855A
High-performance
100 MHz Differential
Amplier
The DA1855A is a stand-alone,
high-performance 100 MHz differential
amplier. It is intended to act as a
signal conditioning preamplier for
oscilloscopes, digitizers and spectrum
analyzers, providing differential
measurement capability to instru-
ments having only a single-ended
input. When used with a DA1855A,
oscilloscopes can obtain Common
Mode Rejection Ratio (CMRR) and
overdrive recovery performance levels
previously unobtainable.
Amplier gain can be set to 1 or 10.
A built-in input attenuator can
be separately set to attenuate
signals by a factor of 10, providing
gains of 10, 1, or 0.1 and common
mode dynamic range of ±15.5 V (÷1)
or ±155 V (÷10). Optional probes
increase the maximum input signal
and common mode ranges in
propor tion to their attenuation ratio but
do not exceed their maximum input
voltage rating. Effective gain of the
DA1855A, including probe attenuation,
amplier gain and attenuator settings,
is automatically displayed.
The DA1855A has a bandwidth of
100 MHz, but any one of the three
3-pole bandwidth limit lters can be
selected to reduce bandwidth to
20 MHz, 1 MHz or 100 kHz to limit
noise above the frequency of interest.
The DA1855A output is carefully
limited to ±500 mV, so that the
oscilloscope is not overdriven by large
inputs. This allows many oscilloscopes
to directly measure the settling of
D/A converters with 14-bit (60 ppm)
precision, better than any other
differential comparator.
The DA1855A features a built-in
Precision Voltage Generator (PVG)
that can be set to any voltage between
±15.5 V (±10 V in Differential Offset.
The PVGs output can be selected as
an input to the inverting (-) input of the
amplier for operation as a differential
Key Features
Full control from oscilloscope through
ProBus interface
DC to 100 MHz bandwidth
Outstanding 100,000: 1 Common
Mode Rejection Ratio (CMRR)
Gain of X1 or X10
Industry-leading overdrive recovery
Low noise
Selectable BW limiting
Two gain control modes when
connected to a Teledyne LeCroy
oscilloscope
Built-in Precision Voltage
Generator (PVG)
Comparator and true
differential offset modes
The DA1855A is a stand-alone, high-performance differential amplier providing the
fastest overdrive recovery of any commercially available product. This unique capability
allows the amplier to make measurements that would normally be limited by oscilloscope
overdrive recovery.
SPECIFICATIONS AND ORDERING INFORMATION
comparator or applied internally as a true differential offset
voltage. The PVG is also available for external use through
a rear panel connector.
The DA1855A operates from 90 to 250 VAC line without
line switching. High-performance differential probes
such as the DXC100 ÷10/÷100 high CMRR probes are
recommended.
Overdrive Recovery
With a ÷100 probe, the DA1855A settles to within
100mV referred to input, from a 400 V input signal
within 100ns. With attenuating probes, this allows
the in circuit measurement of dynamic saturation in switch
mode power converter switching devices.
Comparator Mode
The DA1855A becomes a differential comparator when
the internal PVG output is selected as the amplier’s
inverting (-) input. In this mode, the DA1855A can be used
to measure relatively small signals that are riding on large
AC or DCcomponents (within the precision and accuracy
limitations of the PVG). Therefore, an oscilloscope, when
used with the DA1855A, can make voltage measurements
that are much often more accurate than the oscilloscope is
capable of by itself. The output of the PVG is available for
external use via a rear panel connector.
True Differential Offset Mode
The DA1855A has built-in Precision Voltage Generator
can be used to generate a true differential offset while still
allowing both inputs to be used as differential inputs. The
offset range can be as high as ±50,000 divisions and the
generator has 5 1/2 digit resolution. This mode facilitates
making measurements such as changes to a transistor’s
base to emitter voltage caused by variations in temperature
and/or current. Used in this mode, the voltage generator
can be set to a value that will zero out the static value
of the junction’s on voltage. The DA1855A’s differential
measurement capability will reject any dynamic signal
common to both sides of the junction, and the oscilloscope
is left to measure only the changes in the junction voltage.
Autobalance
Each time either gain setting button is pressed, the
DA1855A automatically adjusts the amplier’s DC balance.
Specications
Main Specications
Bandwidth > 100 MHz
Electrical Characteristics
Rise time (typical) < 3.5 ns
Ordering Information
Product Description Product Code
Differential Ampliers
1 Ch, 100 MHz Differential Amplier DA1855A
with Precision Voltage Source
÷100 or ÷10 Selectable, 250 MHz DXC100A*
Passive Differential Probe Pair
÷1, 50 MHz Passive Differential Probe Pair DXC200*
÷100, 250 MHz 2.5kv, High Voltage Probe Pair DXC-5100*
(requires DA101 for full performance)
Ordering Information (cont’d)
Product Description Product Code
÷10 1 MΩ Passive Attenuator for DXC Series Probes DA101*
2 Ch,100 MHz Differential Amplier DA1855A-PR2
with Precision Voltage Source
DA1855A with Rackmount DA1855A-RM
DA1855A with Rackmount DA1855A-PR2-RM
(must be ordered at time of purchase, no retrot)
*Must be used with DA Series Differential Ampliers
Customer Service
Teledyne LeCroy oscilloscopes and probes are designed, built, and tested
to ensure high reliability. In the unlikely event you experience difculties,
our digital oscilloscopes are fully warranted for three years and our probes
are warranted for one year.
This warranty includes:
• No charge for return shipping • Long-term 7-year support
• Upgrade to latest software at no charge
© 2018 by Teledyne LeCroy, Inc. All rights reserved. Specications, prices, availability, and delivery subject to change
without notice. Product or brand names are trademarks or requested trademarks of their respective holders. da1855a-ds-07feb18
1-800-5-LeCroy
teledynelecroy.com
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