TA2123AF 데이터 시트보기 (PDF) - Toshiba
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TA2123AF Datasheet PDF : 20 Pages
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TA2123AF
(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 Fig.3. And it is smoothed
and detected by DET circuit (pin 36). 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 Fig.4.
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.
20kΩ
28
2R1
2R1
27
20kΩ
PWA 20
31
ATT
R4 = 20kΩ
BST
33
32
PWC 21
C4
34 R2 = 100kΩ
G1(ω)
LPF
A1
G2(ω)
HPF
G3(ω)
A2
BPF
Fig.4 Block diagram of bass boost
10
2002-10-30
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