Fig. 2 indicates frequency response at boost and cut-off.
Response [dB]
Boost
CXA2513M
0dB
• CXA2513M system
VI
ωo s
Q
H (s) =
s2 +
ωo
Q
s + ωo2
Flat
fO =
1
2π √ LC
Cut-off
fO
Fig. 2
Frequency [Hz]
R
Operational amplifier
Vo
R
Z (s) Z (s)
H (s)
Ic
Gm1
Ib
Gm2
Fig. 3
The structure of the graphic equalizer used in this IC is shown on Fig. 3. This circuit performs boost and cut-off
controlled by 2 transconductance amplifiers that can vary the conversion coefficient through control currents Ib,
and Ic around ωo. ("ωo" is center frequency determined by band-pass filter.) Output impedance Z (s) of Gm1,
Gm2 can be expressed as
1
T (s) =
H (s) · Gm1
– 12 –