[sdiy] Outputs grounded! Re: SSI2164 datasheet updated

mskala at ansuz.sooke.bc.ca mskala at ansuz.sooke.bc.ca
Sat Aug 11 20:41:35 CEST 2018

On Sat, 11 Aug 2018, KD KD wrote:
> Most folks dont ground OPAMP, logic's, LM13700 outputs so why suddenly 2164's?
> Do you ground OPAMP outputs and take the chance of sudden system current
> increase despite manufacturers suggestion to leave unused outputs open?

Op amps have voltage outputs, intended to feed into relatively high
impedance.  The 2164 has current outputs, intended to feed into virtual
grounds with relatively low impedance.  If you leave an unused 2164 output
open, it''ll be trying to force current into a place where no current can
go, which probably won't exactly harm anything but will mean some of the
transistors are not at their intended operating points, and it could
affect the performance of the parts of the chip you are using.

The LM13700's OTA outputs are current outputs too and should ideally go
into virtual grounds for best performance, although not all popular
LM13700 circuits do that.  Its buffer outputs are voltage outputs and
should be left open if not used.

Matthew Skala
mskala at ansuz.sooke.bc.ca                 People before principles.

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