带通滤波器(BandpassFilter).DOC

带通滤波器(BandpassFilter)

Basic Filter Circuits

1. High-Pass Filter(高通滤波电路)

3dB Frequency

或

Roll-off Attenuation(衰减斜率)

At low frequencies, ,

or

At (called “Octave” (八度音)，

Roll-off Attenuation (衰减斜率)

At (called “decade” ),

Roll-off Attenuation (衰减斜率)

Phase Shift(相移)

The output voltage, vout, leads ahead of the input voltage, vin, by the angle θ,

where .

At ,

At ,

2. Low-Pass Filter(低通滤波电路)

3dB Frequency

or

Roll-off Attenuation(衰减斜率)

At high frequencies, ,

or

At(Octave(八度音)，

Roll-off Attenuation(衰减斜率)

At,

Roll-off Attenuation (衰减斜率)

(3) Phase Shift(相移)

The output voltage, vout, lags behind the input voltage, vin, by the angle θ,

where .

，

，

3. Band-Pass Filter (带滤波器)

Resonant Frequency (共振频率): ，or

，

Quality factor (质量因数) (sharpness of the bell-shape curve)

At 3dB point，

There are two 3dB points: ω1 and ω2

4. Band-Reject Filter (or called Notch Filter) (带拒滤器)

1

10mH

0.01μF

100Ω

L

C

R

vin

vout

1

0.707

ω

ω1

ω2

ωo=

C

vout

vin

R

L

1.0

0.707

ω

ω1

ω2

ω0

1

0

0

3dB

0

-10

-20

-30

0.1

1

10

or

0

IR

IZ

vC

900

450

00

1

vin

vout

C

R

1

0

0

3dB

0

-10

-20

-30

0.1

1

10

102

IR

IZ

vR

-900

-450

00

1

10

0.1

vin

vout

R

C