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Frequency meter input stage

Discussion in 'Electronic Design' started by Ronald, Dec 21, 2005.

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  1. Ronald

    Ronald Guest

    Hi,

    Ive been trying to make myself a frequency counter for some time. I have
    made a few attempts, but they have usually been more like random number
    generators, because i cant get the input stage right. I dont have much
    experience with analog electronics.

    I though that before wasting my time and money on building the new
    design, maybe some of you could check my latest design out and tell me
    if it is OK or what should i change. The input stage schematic is at :
    www.zone.ee/emzee/freq.PNG
    Or any other ideas for a good input stage?

    My goal would be to get it read up to 100MHz or more and have input
    impedance of 1MOhm.

    Ronald
     
  2. Andrew Holme

    Andrew Holme Guest

    You've got no hysteresis on that comparator - the positive feedback via R6
    is decoupled by C4.

    Have you tried looking at the comparator output on a 'scope?
     
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