TA2160FNG

2004-05-11

7

(b)

AGC circuit

The AGC circuit of bass boost function is realized by the variable impedance circuit. The AGC

DET circuit detects the low frequency level of center amplifier. When this level becomes high,

the variable impedance circuit operates, and this circuit attenuates the input level of center

amplifier.

The AGC DET circuit is the current input, so that the output voltage of ADD amplifier is

changed into the current ingredient by resistor Rb and capacitor C5 which are shown in Figure

2. And it is smoothed and detected by DET circuit (pin 14). And the direct current should not be

applied to the AGC IN circuit, because, as for the circuit, the sensitivity setup is high.

Moreover, the AGC signal level is decreased in case that the resistor R5 is connected with the

capacitor C5 in series. And the AGC point can be changed. But the center amplifier is clipped in

the low frequency in case that the resistor R5 is larger.

(c)

Bass boost

The signal flow of bass boost function is as follows, refer to Figure 3.

LPF (internal resistors 2R1 and external capacitor C1)

→ ATT (variable impedance circuit)

→ HPF (BST amplifier)

→ BPF (LPF: internal resistor R4 and external capacitor C3, HPF: external capacitor C4

and internal resistor R5)

→ Center amplifier

The center amplifier signal becomes the reverse phase, because the phase of audio frequency

range is reversed with two LPFs.

18

PWA

PWB

PWC

19

17

BST

22

23

C4

21

Rd

Rc

C2

C5

Rb

Flow of the bass boost level

20

AGC

DET

ATT

14

24

Ra

Ra

Flow of the bass boost signal

11

8

Figure 2

Bass Boost System