Question about core sense amplifiers
hilpert at cs.ubc.ca
Wed Mar 11 12:22:12 CDT 2015
On 2015-Mar-10, at 8:08 AM, Vincent Slyngstad wrote:
> I've got a technical question about core memories. I've been looking, in particular, at the MC1540G sense amplifier. There's an external capacitor that is supposed to be connected between pins 1 and 10 (it looks like about .01uF was traditional). Maybe I'm being thick this week, but I don't quite get what this does for the circuit. It's part of the "DC restoration" section.
> I think I have some idea what amplification and slicing mean in this context, but "DC restoration" isn't firing any neurons.
> Can any of you that have studied how core works help me understand this?
Looking at the 1540 internals schematic, it looks like a frequency compensation capacitor.
Early op amps like the 709 required external capacitors for freq. comp.
Core sense amps are essentially a form of voltage comparator adapted to respond to the absolute value of a differential input (produce the same output for a voltage difference of either polarity at the inputs), and voltage comparators in turn are essentially op-amps running open-loop.
(if that helps any . . )
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