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Kai Klaas
02/25/06 06:47
Read: 464 times
Germany


 
#110780 - Aha!
Responding to: Sun Din's previous message
I am basically using this network as a level shifter, i.e. to drop a signal from 15V to 4.7V. That is why I am not using the 7805.

Sorry, I misunderstood you all the time. I thought that you want to supply the TTL-chip. Well, level shifting can be done by using a zener or a resistive voltage divider, but due to the rather high input low current (IIL) of 1.6mA of TTL-chip, value(s) of resistor(s) must be very small. It's much better to use an additional transistor stage for this level shifting or to use a HCMOS-chip instead of TTL-chip. Level shifting for HCMOS-chips is much easier.

Kai

List of 21 messages in thread
TopicAuthorDate
Zener Turn-on-time      Sun Din      02/20/06 01:16      
   Remedy        Kai Klaas      02/20/06 07:08      
      Thank You Kai      Sun Din      02/22/06 06:18      
         Divider      Kai Klaas      02/22/06 06:34      
            Resistor values      Sun Din      02/23/06 03:27      
               Read again my calculation example      Kai Klaas      02/23/06 05:58      
               drop that stupid resistor to ground      Erik Malund      02/23/06 07:04      
         can you draw the schematic?      Abhishek Singh      02/22/06 07:21      
            Assistance required to post Sch      Sun Din      02/23/06 03:38      
               If using "Windows"        Jon Ledbetter      02/23/06 07:57      
                  Typo Oops      Jon Ledbetter      02/24/06 08:19      
         Using a cap is enough      Kai Klaas      02/22/06 09:13      
            actually for the "typical" use it is not      Erik Malund      02/22/06 09:53      
               Less than 1nsec      Kai Klaas      02/22/06 10:12      
            Resistor instead of the cap      Sun Din      02/23/06 03:32      
   Sch      Sun Din      02/24/06 04:48      
      ALWAYS design to worst case.      Erik Malund      02/24/06 07:42      
      Homepage      Jon Ledbetter      02/24/06 08:13      
         why is that 1k still there      Erik Malund      02/24/06 08:52      
      Aha!      Kai Klaas      02/25/06 06:47      
         Thank you all for your help.      Sun Din      02/27/06 08:42      

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