[sdiy] Question about tri-state buffers and encoders

Roman Sowa modular at go2.pl
Tue Sep 12 10:19:05 CEST 2023

What's the difference? If there are pull-ups, you're "fighting the 
resistors" when signal goes low as well. Same load. Especially since all 
logic families invented during last 40 years have symetrcical current 
capacity in H and L state.


W dniu 2023-09-11 o 21:55, Jay Schwichtenberg via Synth-diy pisze:
> As mentioned tri-state is typically used for buses. You don't want to 
> use pull-downs on those. You use pull-ups to keep the bus from floating. 
> If you use pull-downs you're fighting the resistors when the signals go 
> high. If you use a high resistance with pull-downs with CMOS it will 
> probably work. If you use a lower resistance then you may not be able to 
> pull the signal high when needed.
> Jay S.
> On 9/10/2023 12:47 PM, David G Dixon via Synth-diy wrote:
>> My second question is, even though the circuit works with just the 
>> unconnected encoder inputs grounded, should I install pull-down 
>> resistors to ground onto all of the buffer outputs anyway, just to be 
>> safe?
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