NE5538

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Joined 2010
I just found in an old Panasonic car amplifier two of these op-amps made by Signetics looking absolutely identical to NE5532...60v/us slew rate for a minimum gain of 5x...Does anyone have more info on this apart from the datasheet?
 

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Dual version of NE538. Much higher voltage noise than 5532, 30nV/√Hz, lower bandwidth 6MHz, much lower current noise (about 0.15pA/√Hz from the graph - bias current is low as 65nA). Noise-wise its matched to 100k or above which is unusual for bipolar.

Most of the voltage noise is probably due to the unusual topology with resistors in the input section. This allows the inputs to be very different voltages (they even recommend using it as a comparator).

There appears to be no relationship between these chips and the 5532/5534 at all.