An electronic circuit receives noise from switching element. If voltage on the switching device swings from 4 volt to 6 volt within 100 microsecond, during which current makes a transition from 10 microampere to 25 microampere in 10 nanoseconds, what might be the noise coupling mechanism? Identify it using suitable calculations.

Initial voltage, V₀ = 4V
Final voltage, V₁ = 6V
Change in voltage, dv = 6 - 4 = 2V
Initial current, I₀ = 10μA = 10×10⁻⁶ A
Final current, I₁ = 25μA = 25×10⁻⁶ A
Change in current, di = (25 - 10)×10⁻⁶ A = 15×10⁻⁶ATime interval, dt = 10ns = 10×10⁻⁹s = 10⁻⁸s

dv
         
dt   =   
  2V
         
10⁻⁸s    = 2×10⁸ V/s
 

di
         
dt   =   
  15×10⁻⁶A
         
10⁻⁸s   =   15×10² A/s
 

Pseudo impedance is given by,

Pseudo impedance =   
  dv/dt
         
di/dt

=   
  2×10⁸ V/s
         
15×10² A/s    = 0.0133 Ω
 

  Pseudo impedance = 0.01333 Ω .
As, 0.01333<<377
This reveals that the noise is coupled via inductive coupling mechanism .