Ignition questions & the Nat semi Injector driver

[Doug Rorem]

Jim,

Well this art isn't much better, but here's where you want to place
your fast recovery diode (switches on from a reverse bias condition
very quickly).. This provides a path for the current to keep flowing
in the coil after the transistor turns off [the coil wants to keep current
constant]. Without something like this, the coil can create very large
voltages and cause the transistor to break down.

  +12
   |
   |------
   |     |
 -----   c
  / \    o
  | |    i
  ---    l
   |     |
   -------
      |
  transistor
    switch
      |
      |
     gnd


--
Doug Rorem
University of Illinois at Chicago         (312)-996-5439  [voice]
EECS Department  RM 1120                  (312)-413-1065  [fax]
851 S. Morgan Street                      (708)-996-2226  [pager]
Chicago, IL 60607-7053                    rorem at uic.edu