I am currently working on a project that involves designing some front end electronics that shape the charge pulse from a solid state detector (effectively a current source - I1 on the diagram). Our source produces a pulse that is about 10us long. The design is essentially a charge sensitive preamplifier, followed by pole zero, followed by two Sallen-Key filters in a low pass configuration that act as shaping. I have a circuit schematic enter image description here that works, however I should like the outcoming voltage pulse over the load (R13) to be longer. Currently, the pulse is semi-gaussian and lasts for about 200-300us. If I could double or triple this time it would work better with the readout electronics. I would also be interested to know if what i have done is correct, as I don't have a background in electronics so there may be bare faced errors in the design.

On final question on this topic is this - what is the best way to increase the height of the voltage pulse, while keeping the noise to a minimum? I can do this by changing R9 or R10, however I am wondering if there is a better way to do this. enter image description here

  • \$\begingroup\$ Can you show the waveforms of what you have and what you want? \$\endgroup\$
    – winny
    Jul 3, 2017 at 13:15
  • \$\begingroup\$ imgur.com/a/UvWo9 is what i have currently. I'd like to double or even triple the width of the resulting pulse \$\endgroup\$
    – Tom
    Jul 3, 2017 at 13:19
  • \$\begingroup\$ Please show how you want R13 voltage to look like. \$\endgroup\$
    – winny
    Jul 3, 2017 at 14:01
  • \$\begingroup\$ exactly the same, but the pulse should last about 500us, not 200us \$\endgroup\$
    – Tom
    Jul 3, 2017 at 14:03
  • 1
    \$\begingroup\$ Is the shape of the trailing edge important? \$\endgroup\$ Jul 3, 2017 at 15:14

1 Answer 1


Simply use a peak-hold. Which feeds an analog comparator. Which triggers the ADC and the reset-delay. And use a 74122/123 delay IC, to reset the peak-hold after 1milliSecond.


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