While Gas Discharge Tubes (GDTs) are a popular choice to protect high frequency circuits in electronic equipment, there are many circuits that can be sensitive to capacitance. This issue can definitely affect filter or input matching networks making it important for designers to have accurate capacitance measurements when developing their applications. A key consideration to ensure GDT measurements are accurate is that typical industry capacitance measurements at 1 MHz often times are not sufficient to capture the behavior or actual capacitance of a high frequency circuit operating at 2 GHz or higher.
Understanding the requirement for precise data and as a helpful guide, we’ve developed an application note that provides a testing procedure for capacitance. It uses an example comparing the results of a Bourns® Model GDT25 (2-element) GDT and our latest next-generation GDT, Bourns® Model GDT35 (3-element) components. The app note outlines various test procedure techniques that our engineers found to be very useful for obtaining accurate capacitance values.
The app note also highlights the importance of performing component tolerance analysis on the circuit to help ensure that the design is stable. It includes measured data and real results from a sampling of GDTs.
The ultimate goal in recommending a proven procedure to obtain accurate GDT capacitance measurements and tests is to help designers achieve state-of-the-art performance and application stability. Our tests showed how often capacitance variations during design, tooling and manufacturing processes were experienced. We believe this app note is an excellent resource in the design process that aids in determining the right level of protection given the increase in new electronic equipment that use high frequency circuits.