# Cut-off or Corner Frequency

Discussion in 'Homework Help' started by kaname08, Feb 11, 2012.

1. ### kaname08 Thread Starter Member

Sep 22, 2010
37
0
HI everyone, i really really need your help guys, we are about to do a small signal amplifier, but i need to know what coupling and bypass capacitor to use,so in order for me to solve it i need to know the corner or cut-off frequency to be used base on this formula :

Ce2 = 1/(2*pi * FL * Xce2)

pls help me guys,how will i get the frequency??,,,,

2. ### Audioguru New Member

Dec 20, 2007
9,411
896
One capacitor in the signal circuit reduces the output -3dB (x 0.707) which is called the cutoff frequency. Two capacitors (an input capacitor and an output capacitor) cause a reduction of -6dB so their values must be doubled for the entire amplifier to have the required low cutoff frequency.
The formula for frequency is 1/2 x pi x RC.

3. ### crutschow Expert

Mar 14, 2008
13,529
3,393
To clarify, that should be 1/(2 x pi x RC).

4. ### kaname08 Thread Starter Member

Sep 22, 2010
37
0
but i still dont have a Capacitance and where will i get this resistor??

5. ### Audioguru New Member

Dec 20, 2007
9,411
896
You use simple arithmatic to calculate the resistor and capacitor values. Then you buy them.