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Preamble DA1855: Difference between revisions
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[[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. 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 1800 series differential amplifiers. | [[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. 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 1800 series differential amplifiers. | ||
In general, any instrument that has a slideback (aka comparison) voltage will behave in overdrive better than other amplifiers. The Tektronix [[1A7A]] and [[7A22]] were not very fast (1 MHz), but used feedback circuitry that recovered very well within their bandwidth. Their available offset voltage was differential, allowing true differential performance over a limited range (1 V at the most sensitive range), but the offset was not calibrated. The 1A7A (designed by [[Thor Hallen]]) and the 7A22 (designed by [[Val Garuts]]) used essentially the same circuit. Exactly who came up with the brilliant input circuit is lost to history. The 1A7A came out first, but Thor had worked as evaluation engineer for Val Garuts. Val does not remember who created the circuit, and Thor died in 2002. | In general, any instrument that has a slideback (aka comparison) voltage will behave in overdrive better than other amplifiers. The Tektronix [[1A7A]] and [[7A22]] were not very fast (1 MHz), but used feedback circuitry that recovered very well within their bandwidth. Their available offset voltage was differential, allowing true differential performance over a limited range (1 V at the most sensitive range), but the offset was not calibrated. The 1A7A (designed by [[Thor Hallen]]) and the 7A22 (designed by [[Val Garuts]]) used essentially the same circuit. Exactly who came up with the brilliant input circuit is lost to history however, Val thinks it may have come from an HP design. The 1A7A came out first, but Thor had worked as evaluation engineer for Val Garuts. Val does not remember who created the circuit, and Thor died in 2002. | ||
I designed the [[1A7]] (using Nuvistors) and will take credit for the combination of features of the 1A7A and 7A22, but the circuitry of the 1A7A and 7A22 is far superior and used the much more stable JFETs input devices. | I designed the [[1A7]] (using Nuvistors) and will take credit for the combination of features of the 1A7A and 7A22, but the circuitry of the 1A7A and 7A22 is far superior and used the much more stable JFETs input devices. | ||
John Addis | John Addis | ||
November 16, 2018 | November 16, 2018; updated 8/18/2024 | ||
</blockquote> | </blockquote> | ||