From: petrus.bitbyter@hotmail.com   
      
   "Computer Nerd Kev"  schreef in bericht   
   news:XnsA22BE939DAB09CSKJHNMW985780A@94.75.214.90...   
   > Yep, the load on the output buffer transistor will be 1mA   
   > max., so the current required to drive it can be kept well   
   > within spec.. The resistors used can therefore be of high   
   > enough values to keep the currents between outputs very low.   
   > This is what I meant by my situation perhaps fitting with the   
   > "special cases" statement in the book.   
   >   
   > I was mainly wondering if there was anything wrong with adding   
   > current from multiple high outputs in this manner. I   
   > understand the totem-pole circuit, but I wondered if something   
   > in the IC circuit as a whole might be problematic in this   
   > application.   
   >   
   > Perhaps I'm too cautious and I should just build the thing and   
   > find out (which is probably what I'll do). On the other hand I   
   > though it was worth a question in case I was missing something   
   > already known.   
   >   
   > --   
   > __          __   
   > #_ < |\| |< _#   
      
   Expect you'll find it not to work out the way you want to. The old standard   
   TTL can source less then 0.5mA though sink about 8mA. Newer LS do not do   
   better. CMOS differs a lot but is not the same for all types. At least for   
   TTL you have to realise that the output resistance for a high output is way   
   much higher then for a low. You can work around a bit by using pull up   
   resistors but it'll take quite some time to calculate the various resistors   
   and even more time for experimentally fine tuning.   
      
   petrus bitbyter   
      
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