Lecroy DA1855A Differential Amplifier

Overview

The Lecroy DA1855A is a high-performance 100 MHz differential amplifier designed as a signal conditioning preamplifier for oscilloscopes, digitizers, and spectrum analyzers. It provides differential measurement capability to instruments with single-ended inputs, enabling Common Mode Rejection Ratio (CMRR) and overload recovery performance previously unobtainable with standard oscilloscope inputs.

Key Features

• 100 MHz bandwidth with selectable bandwidth limit filters (20 MHz, 1 MHz, 100 kHz)
• Selectable gain: 1 or 10
• Built-in 10x input attenuator for effective gains of 10, 1, or 0.1
• Common mode input range: ±15.5 V (÷1) or ±155 V (÷10)
• Output limited to ±500 mV to prevent oscilloscope overdriving
• Built-in Precision Voltage Generator (PVG) for offset and comparator operation
• Automatic DC balance adjustment on gain changes
• Rapid overload recovery: settles to 100 mV within 100 ns (÷100 probe from 400 V input)
• Operates on 90-250 VAC without line switching

Applications

• High-precision differential signal measurement
• Power supply and converter switching dynamics characterization
• Differential signal conditioning for oscilloscopes and spectrum analyzers
• Low-level signal measurement on large AC or DC backgrounds
• Transistor junction voltage temperature and current coefficient testing