—10—

CXA1352AS

Here, using

ωo and Q we can express BPF transmittance H (s) as

Z (s) =

Q

s+

1

+

ωo • Q

ωo • Gm1

Gm1

Gm1 • s

This formula shows that this system and the aforementioned LCR circuit have equivalent impedance

characteristics on Z (s).

Then, regarding Gm as the maximum value of Gm1 and Gm2, the operation can be observed as follows.

Maximum cut occurs when Gm1=Gm and Gm2=0. At that time we have transmittance T (s) as

T (s) =

Z (s)

=

Z (s) +R

This is equal to the frequency characteristics of the conventional graphic equalizer at cut.

Also, maximum boost occurs when Gm1=0 and Gm2=Gm. At that time we have transmittance T (s) as

T (s) =

Z (s) +R

=

Z (s)

This is equal to the frequency characteristics of the conventional graphic equalizer at boost.

We can then deduce that, as far as the operation is concerned the graphic equalizer on this IC and the

conventional graphic equalizer are equal, even when the system differs. The merit in using this IC’s system

rests with the fact that monolithic filter technology realizes a graphic equalizer without external parts.

The structure of the actual graphic equalizer, including BPF, is shown on Fig. 4.

Fig. 4

H (s) =

ωo

• s

Q

ωo

s +

Q

ωo

• s +

Q

(1+R • Gm) •

• s+

Q

ωo

• s +

Q

(1+R • Gm) •

• s+

Q

R2

30k

SUM

Gm4

Gm3

Gm1

I CUT

I BOOST

GND

GND

GND

GND

GND

C2

C1

C3

Gm2

VI

1

1

R1

30k