I try to calculate the corner frequency of an RC lowpass in but the result I'm getting is wrong. Here's what I did:
R=17k, C=15n
The lowpass is basically a voltage divider, hence Vout=Vin*Z/Xc
rearrange: Vout/Vin=Z/Xc
The corner frequency is where the voltage drops by sqrt(2) (and power by half):
1/sqrt(2)=Z/Xc
reactance Xc is 1/wC
impedance Z:
Z=17k-jXc=17k-j(1/wC)
substitute:
1/sqrt(2)=(17k-j(1/wC)) / (-j(1/wC))
solve for w:
w=-j(sqrt(2)-2)*(1000/51)=-j1148.60
f=w/(2*pi)=182.806i
to polar: 182.806 Hz<90°
The actual corner frequency is 624.1 Hz
what am I doing wrong? how to do it properly?
R=17k, C=15n
The lowpass is basically a voltage divider, hence Vout=Vin*Z/Xc
rearrange: Vout/Vin=Z/Xc
The corner frequency is where the voltage drops by sqrt(2) (and power by half):
1/sqrt(2)=Z/Xc
reactance Xc is 1/wC
impedance Z:
Z=17k-jXc=17k-j(1/wC)
substitute:
1/sqrt(2)=(17k-j(1/wC)) / (-j(1/wC))
solve for w:
w=-j(sqrt(2)-2)*(1000/51)=-j1148.60
f=w/(2*pi)=182.806i
to polar: 182.806 Hz<90°
The actual corner frequency is 624.1 Hz
what am I doing wrong? how to do it properly?