So given this problem:

circuit http://imagizer.imageshack.us/v2/640x480q90/902/1FzzwZ.png

The correct bode plot for it is:

bode plot http://imagizer.imageshack.us/v2/640x480q90/661/yILL19.png

What I don't understand is how the -3db was measured. I know that -3db can be found through 20log(1/sqrt(2)), but how is it measured right at frequency 10kHz?

## Best Answer

Be careful, the x-axis is not frequency but radian frequency. So the break-point frequency is not 10 kHz but 10 krad/s.

Now you have the transfer function \$T(\omega)=\dfrac{1}{1+j\omega{}RC}\$ in your top picture. What is the absolute value of that function when \$\omega=1/RC\$?

What is \$1/RC\$ when R is 100 ohms and C is 1 uF?