LeCroy DA1855A Overview

Overview

DA1855A-OM-E Rev A

ISSUED: July 2002

2-1

2

Overview

DESCRIPTION

The DA1855A is a stand-alone high performance 100 MHz 

differential amplifier. It is intended to act as signal conditioning 

preamplifier for oscilloscopes, spectrum analyzers and other 

instruments, providing differential measurement capability to 

instruments having only a single-ended input. When used with a 

DA1855A, high quality oscilloscopes can obtain common mode 

rejection and overdrive recovery performance that was previously 

unobtainable in any product.

When used with a LeCroy oscilloscope equipped with ProBus 

interface, the DA1855A can be controlled through the 

oscilloscope user interface or remote commands.

When used with non ProBus oscilloscopes, the DA1855A 

settings can be controlled directly through the front panel 

controls.

Amplifier gain may be set to 1 or 10. A built-in input attenuator 

may be separately set to attenuate signals by a factor of 10, 

allowing 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 proportion to 

their attenuation ratio, but not exceeding their maximum input 

voltage rating. Effective gain of the DA1855A, including probe 

attenuation, amplifier 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 filters may 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 limited at 

±

 500 mV so that the 

oscilloscope is not overdriven by large inputs. This allows an 

oscilloscope to directly measure the settling of D/A converters 

with 14 bit (60ppm) precision.

The DA1855A features a built-in Precision Voltage Generator 

(PVG) that can be set to any voltage between 

 ±

 15.5 Volt (

±

 10 

Volt in Differential Offset mode) with 5-1/2 digit resolution. Each 

digit of the voltage generator output can be individually 

incremented or decremented. Positive or negative polarity can be 

selected. The PVG’s output can be selected as an input to the