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Entry  Thu Apr 25 20:24:27 2019, anchal, Summary, Electronics Equipment, Adjustable TTL Trigger Generator Box Adjustable_TTL_Trigger_Generator_Box.pdf
    Reply  Sun Apr 28 22:29:18 2019, rana, Summary, Electronics Equipment, should I use an OpAmp as a Comparator? 
       Reply  Tue Apr 30 18:55:06 2019, anchal, Summary, Electronics Equipment, Follow up on TTL Trigger generator box 
Message ID: 2327     Entry time: Thu Apr 25 20:24:27 2019     Reply to this: 2329
Author: anchal 
Type: Summary 
Category: Electronics Equipment 
Subject: Adjustable TTL Trigger Generator Box 

Today I made a standalone Adjustable TTL Trigger generator box. Following are some features:

  • The rising edge of output can be used to trigger all TTL compliant external trigger enabled equipment (oscilloscopes, HP4395A, SR785 etc.)
  • Uses AD620 at very high gain (G=5k) to create a comparator. Positive input is the signal and negative input is controlled with a 100 kOhm potentiometer.
  • The threshold can be set anywhere between +18V and -18V.
  • Powered internally with four 9V Alkaline batteries and has a switch to turn ON/OFF. Should last really long.
  • The output is through a 4.7 V Zener Diode which activates in reverse bias when the signal becomes 140 uV higher than the set threshold.
  • Input impedance equivalent to AD620.
  • The trigger is not latched and output goes to -0.7 as soon as the signal falls below the threshold.
  • Has a window port for checking the threshold.
  • The practical way of operating would be to see the signal and output of the box together in an oscilloscope first and fine tune the potentiometer to see triggers at the right point.
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