Understanding High Pass Filter: Plate Behavior and Phase Shift

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SUMMARY

The discussion focuses on the behavior of a high pass filter circuit, specifically the interaction between a capacitor and a resistor. At frequencies significantly above the corner frequency, the output voltage (Vout) on the capacitor's opposite plate closely follows the input voltage without any phase shift. This behavior is crucial for understanding the rapid voltage changes across the capacitor, which are governed by the relationship i = C dV/dt, where larger currents cannot be supported by the resistor if the output does not track the input accurately.

PREREQUISITES
  • Understanding of high pass filter circuits
  • Familiarity with capacitors and resistors in electrical engineering
  • Knowledge of voltage, current, and their relationships in circuits
  • Basic grasp of sine wave signals and frequency concepts
NEXT STEPS
  • Study the principles of capacitor behavior in AC circuits
  • Learn about the mathematical derivation of high pass filter transfer functions
  • Explore the concept of corner frequency in filter design
  • Investigate the effects of resistor values on filter performance
USEFUL FOR

Electrical engineers, students studying circuit design, and anyone interested in the dynamics of high pass filters and their applications in signal processing.

d.arbitman
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I'm having a hard time visualizing what happens on the plates of the capacitor in series with a resistor in a high pass filter circuit. When the input to the capacitor is high, assuming a sine wave (say +5V) what happens on the opposite plate of the capacitor (Vout)? Should the output follow the input (ie. is there no phase shift)?
 
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d.arbitman
At frequencies much higher than the corner frequency, the output side of the capacitor will follow the input side with no phase difference (in the limit). Imagine a very rapid change of voltage on the input side of the capacitor. If the output did not follow this rapid change then we would have created a rapid change in voltage *across* the capacitor (dV/dt) which, in turn, would imply larger current (i = C dV/dt) than can be supported by the resistor.
 

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