I do not think the designer was considering noise at all because tying the inputs together would not do anything useful. Emitter resistance is inversely proportional to emitter current (26/mA) but putting them in parallel lowers the current through each emitter so the total emitter resistance stays the same.
Supply current is separate for each TTL gate so by using a single 8-input part, total power it is about half that of a dual 4-input part and a quarter of a quad 2-input part depending on the exact operating conditions. Unused *outputs* should be high for lowest power. 74S30 Single 8-Input 5mA 10mA 74S20 Dual 4-Input 8mA 18mA 74S00 Quad 2-Input 16mA 36mA One clever design I ran across used the 7420 dual 4-input NAND pinout but wired the inputs which are pin compatible so the 7400 quad 2-input pinout would also work. This allows using a 74x00, 74x20, or 74S120 dual 4-input NAND buffer but it draws even more power. 74S120 Dual 4-Input 18mA 44mA On Fri, 28 Oct 2016 13:31:38 -0400, you wrote: >I wounder if originally the designer was hoping to use all 8 wire or'd >inputs to lower the input referred noise during midscale transition. Then >backed out later for some reason. > >On Fri, Oct 28, 2016 at 1:03 PM, Scott Stobbe <[email protected]> >wrote: > >> Could also be a quirk about the 74S30 that gives it better phase noise >> over a basic buffer. >> >> >> On Friday, 28 October 2016, jimlux <[email protected]> wrote: >> >>> On 10/28/16 9:13 AM, Scott Stobbe wrote: >>> >>>> The OCXO82-59 datasheet lists 12V supply, 5V clock out, could also be a >>>> blown regulator in your ocxo, if it is indeed a 12v model. >>>> >>>> There you go..the design could use a 74S30 as a driver - it's fast, >>> fairly good drive, but runs off 5V. If the regulator is shorted, and you >>> put 12V on it, it will cook. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
