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1A7: Difference between revisions
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====Origins==== | ====Origins==== | ||
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[[John Addis]] says: | |||
Type [[D]] was a mid-1950s DC-coupled 1 mV/div differential plugin (350 kHz at 1 mV/div, but 2 MHz at 50 mV/div) for the 530 and 540 series of mainframes. Similarly, Type [[E]] was a mid-1950s AC-coupled 50 μV/div differential plugin (30 kHz at 50 μV/div, but 60 kHz at 0.5 mV/div). | Type [[D]] was a mid-1950s DC-coupled 1 mV/div differential plugin (350 kHz at 1 mV/div, but 2 MHz at 50 mV/div) for the 530 and 540 series of mainframes. Similarly, Type [[E]] was a mid-1950s AC-coupled 50 μV/div differential plugin (30 kHz at 50 μV/div, but 60 kHz at 0.5 mV/div). | ||
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Nevertheless, the exact combination of features of the 1A7 was repeated in the 1A7A (designed by [[Thor Hallen]]), in the venerable [[7A22]] (designed by [[Val Garuts]]), and in the [[3A9]] (with additional current probe input). These later three plugins made use of JFETs and all three are of the same design. That circuit, using feedback, is much better than the earlier 1A7 design. | Nevertheless, the exact combination of features of the 1A7 was repeated in the 1A7A (designed by [[Thor Hallen]]), in the venerable [[7A22]] (designed by [[Val Garuts]]), and in the [[3A9]] (with additional current probe input). These later three plugins made use of JFETs and all three are of the same design. That circuit, using feedback, is much better than the earlier 1A7 design. | ||
( | (Correspondence May 2021) | ||
</blockquote> | </blockquote> | ||