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Selecting a Transistor for Sample and Hold Circuit

  1. Nov 10, 2013 #1
    This is my first time here on this forum. I am building an analog to digital converter. It will be running at a frequency of 12MHz and the sample and hold circuit will be 1/8th of that or 1.5MHz. This will be an 8-bit converter and Vdd will be 5 volts. I have a few parts to workout, the sample and hold circuit, comparator, and connectors to the analog input and digital output. I need to select transistors for the sample and hold circuit. I'd just like some help on how to select a transistor for my project. Below is a photo of the circuit I plan to use. The switch will be a transmission gate CMOS switch. I need to find a transistor for this switch with low capacitance in the right place. Also, need several more transistors for the amplifiers. Since, I plan to use these transistors on both a breadboard and PCB, I'll need one that's available in both through hole and SMD types. There are so many transistors to choose from that I don't know if I can find better than whatever one I find. I hope you guys can point me in the right direction to finding one via Mouser or Digikey.

    I hope to use this circuit for actual projects in the future. The particular design I choose for this was for the speed, low power dissipation, wide bandwidth, high input impediance, and low output impediance.

    Thank you in advance for your help,
    Mike
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  2. jcsd
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