Tektronix 11A72 vs 11A52 by EG&G
EG&G's Los Alamos Operations group published a report in 1990 where they evaluated the Tektronix 11A52 and 11A72 in a DSA602
Regarding this report, John Addis commented:
The 11A52 does fairly well in this comparison, particularly in low frequency VSWR/TDR and in noise. The differences between the two plugins are due to two factors:
- The 11A52 uses feedback amplifiers while the 11A72 uses junction error correction circuitry.
- The 11A52 was built using the SH3 IC process while the 11A72 uses a later, faster SHπ IC process.
The 11A52 “Fast recovery time”, as I noted in my Electronics Engineering article refers to the ability to recover without long thermal tails in the millisecond region present in just about everything else. A straight forward brute force amplifier like the 11A72 does recover faster in the ns region. (About 2ns vs 8ns in these tests, although those numbers are difficult to read off the graphs presented). The faster plugins with M377 (11A32, 11A34, 11A52) have a recovery time that depends strongly on the HF ADJ control setting, something the paper does not consider.
I would like to point out that while the 11A52 is feature rich (large dc offset, variable gain control, 1mV/div, 2mV/div, and 5mV/div sensitivities, and two bandwidth limit filters, the 11A72 is feature poor, having none of these capabilities. The M377 IC used in the 11A52 is also more general purpose, having only one high frequency adjustment per channel in all its plugins except the 11A52. The 11A52 has a single software adjustable high frequency adjustment per channel, but it is adjustable separately for each of the 6 switched gain settings.