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Jim Keith

Jim Keith is a senior engineer with Bell-Mark. He received an ASEE from the Wentworth Institute of Technology, Boston, Mass., and a BS in missionary radio technology from the Moody Bible Institute, Chicago, Ill.


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Author Articles

  • Adjustment-Free Fan Controller For Under $1

    By Jim Keith, December 07, 2009

    Circuit activates a cooling fan when the temperature of a target high-power-dissipation device, such as a processor chip, exceeds a predetermined limit. It uses an Epcos PTC Temperature Limit Sensor

  • Charge-Pump VCO Increases Parts Count But Saves On Cost

    By Jim Keith, June 11, 2009

    This charge-pump voltagecontrolled oscillator (VCO) has a number of neat features: single positive power-supply operation, positive VCO reference voltage, fast response, high linearity, temperature compensation, and open collector out

  • Confidently Calculate Rectifier Input Capacitors

    By Jim Keith, March 17, 2005

    A rectifier input capacitor's size is often considered nebulous. Therefore, common practice is to pick a large size, and if the ripple voltage is low enough, all is okay (see the figure, a). If not, it can be increased in size. Other attempts someti