Calculating Low-Pass Filter Corner Frequency for LR Circuit

[VinnyCee]

Homework Statement

Show that a series LR circuit is a Low Pass filter if the output is taken across the resistor. Calculate the corner frequency, f_c, if L = 2mH and R = 10k\Omega.

Homework Equations

H(\omega)\,=\,\frac{V_0(t)}{V_i(t)}

H\left(\omega_c\right)\,=\,\frac{1}{\sqrt{2}}

f\,=\,\frac{\omega}{2\pi}

The Attempt at a Solution

H(\omega)\,=\,\frac{R}{R\,+\,j\omega L}

H(0)\,=\,1

H(\infty)\,=\,0

That does the "show" part. But now I don't know how to get the corner frequency.

\frac{1}{\sqrt{2}}\,=\,\frac{R}{R\,+\,j\omega L}

 

[VinnyCee]

Never mind! It's 796 kHz.

 

[denverdoc]

Per your post on Bode plots, this transfer function would be written as:

1/(1+jwL/R), you might want to plot this before tackling that much more complicated function, if you haven't done simple ones yet.