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Kai Klaas
02/20/06 07:08
Read: 490 times
Germany


 
Msg Score: +1
 +1 Good Answer/Helpful
#110333 - Remedy
Responding to: Sun Din's previous message
Sun said:
I plan to use a cap in parallel with the zener, hence forming an RC network with the series resistor.

Yes, that's the remedy! Zeners can need several hundreds of nanoseconds to turn-on. Zeners can also turn-on slowly because of their parasitic junction capacitance, which is about 100pF even for a tiny BZX55-C4V7. In combination with a relevant source impedance this also leads to a turn-on delay.
Zeners are not suited to protect against ESD for instance, because the turn-on time is way too long. In such cases a transzorb should be used.

Don't worry about turn-on time in your case. Take an electrolytic capacitor or another cap in the F range and you will not have any problems.

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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