Preamble DA1855: Difference between revisions

However, the common mode dynamic range of the M377 is only about ±3.5 V.  So the 11A33 uses a separate IC in front of its M377 with totem-poled input devices to obtain about 8.5 V of overdrive and common mode dynamic range using the same 15 V IC process.  Bandwidth is 150 MHz with four pole BWL filters at 100 MHz and 20 MHz.  The 11A33 was the first differential amplifier with calibrated true differential offset.  [[Pat Quinn]] designed the input IC.  The 11A33 had a redesign shortly after introduction.  I think the redesign may have used the later [[SHPi]] IC process which had p-channel JFETs, but the same 15 V breakdown.  The redesign was done by [[Rich Huard]].  Within the limitation of 8.5 V overload and common mode dynamic range, the 11A33 had, I think, the best overdrive recovery ever, but with limited common mode dynamic range.

[[Preamble Instruments]] was a small start-up eventually employing 28 people.  Products included the 1820, 1822, 1850, 1855, 1820A, 1822A, 1850A and 1855A differential amplifiers and several active and passive differential probes.  (The 1800 series A versions had μP-controlled operation designed by [[Stan Sasaki]] and oven heater that only ran with power on).  The 1850, 1850A, 1855, 1855A (introduced in 1996) used input circuitry based on the M377.  The design used all discrete circuitry and therefore could not quite match the 11A33 for thermals, but its 16 V overload and common mode dynamic range, true differential calibrated offset, along with 10 MHz, 1 MHz, and 100 kHz BWL filters made it very popular.  [[LeCroy Corporation]] bought Preamble Instruments in October 1997 primarily to be able to add the 1855 to its product line.  It changed the model name to DA1855A.  LeCroy is now known as TELEDYNE LECROY.  The DA1855A is still in their catalog as of this writing in November 2018.  Twenty-two years is a good lifetime.  I designed the M377 and the 1850 series differential amplifiers.