AN5270 Просмотр технического описания (PDF) - Panasonic Corporation

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производитель

AN5270

4.3 W ×1(8Ω) Power Amplifier with Volume Control and Tone Control

Panasonic Corporation 

ICs for Audio Common Use

AN5270

s Technical Information (continued)

• Structure of pre-amp. stage (continued)

GF amp., the flat-amp., amplifies the signal equally for all frequencies in the range of 20 Hz to 70 kHz.

GT amp., the treble or tone-amp., has an internal LPF connected to its inverting input. The non-inverting input of GT

amp. is connected to the input signal. Thus, the output of GT passes only the upper range of frequencies (cut-off

frequency = 2.5 kHz).

GB amp., the bass-amp., amplifies the lower range of frequencies. Its cut-off frequency is determined by R1· C1.

If LF pin is left open, then GB amp. has no effect on the overall frequency response.

• Gain calculation

General formula for gain of pre-amp. is (when vol. = max., tone = max.) :

Gpre = GL1 · (GF + GT) − GB · GL2

By vector analysis as shown in fig. Vector diagram of Gpre,

GV [dB] = Gpre + GP

GV [dB] = 20 log √[GL1 · (GF + GT) − GB · GL2 · cosθ]2 + (GB · GL2 · sinθ)2 + GP

where GL1 = 0.5

GF = 1.3

GB = 5.4

Gpre

 0 for (100 Hz)

GT =  1.3 for (1 kHz)

 2.5 for (10 kHz)

GP = 25 dB

Z3 · 0.848

GB ≈ Z3 + R1

θ

GL1 · (GF + GT)

Z3 =

6600

√1 + (2πf · C1 · 6600)2

θ = −tan−1 (2πf · C1 · 6600)

GB · GL2

Fig. Vector diagram of Gpre

GV

G1

*1

−3 dB

G2

G1 : Gain at 100 Hz

G2 : Gain at 1 kHz

G3 : Gain at 10 kHz

f1 : High frequency cut-off when Pin3 is open.

f2 : Low frequency cut-off

G3

−3 dB

Tone = max.

Tone = min.

f

100 Hz f2

1 kHz f1

10 kHz

Fig. Frequency response of AN5270

Note) *1 : This is the response if LF pin is open (i.e. R1 open).

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