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Insights from Spice

Insights from Spice. Adding Capacitance to Attenuation Resistors. Schematic with Resistor Capacitances. 1 meter of coax. Everything to the right of the 50 W resistor is on mezzanine. 5ns pulse with 1ns rise and fall. Effect of Resistor Capacitance. Without Capacitance.

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Insights from Spice

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  1. Insights fromSpice Adding Capacitance to Attenuation Resistors

  2. Schematic with Resistor Capacitances 1 meter of coax Everything to the right of the 50 W resistor is on mezzanine. 5ns pulse with 1ns rise and fall

  3. Effect of Resistor Capacitance

  4. Without Capacitance

  5. Schematic with Resistor Capacitance Same sweep of capacitance 1pF to 15pF

  6. Amplitude Impacted by Capacitance

  7. No Resistor Capacitance

  8. Capacitance Growth with Cell Count • Look at Ceff for: • 1 x 1 cell (single) • 3 x 3 cells where lines couple to other cells • 5 x 5 cells to examine growth with n2 cells • Clearly the absolute value of Ceffdepends on the line capacitance as well as the cell value.

  9. One Cell Sub-circuit Cx = 38fF CapSnO2Line = 15fF CapNiLine = 22fF

  10. Inject Charge Examine Voltage Current = 25mA for 200pS = 5000fC Voltage = 38.6V 130fF impied Note: All Capacitances outside the celll are 0 Note: All Inductors are 0

  11. 1 x 1 and 5x5 Results • For 1 x 1 cell the only capacitor is Cx = 38fF • After all the trouble to simulate, I got the obvious • For 3 x 3 cells the details are above • 5000fC yields 38.6V drop, Ceff = 130fF • For 5 x 5 cells the details are: • 5000fC yields 26V drop, Ceff = 192fF • Note: all these used Cline = 22fF & 15fF • Lines of different width & separation

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