AN618 Panasonic Semiconductor, AN618 Datasheet - Page 14

• Manufacturer Part Number: AN618
• Description: Recording and playing amplifier IC for answering telephones
• Manufacturer: Panasonic Semiconductor

(4) MF Mode
3–2 Setting the Receiver System
below.
4–1 Setting the MF Signal Gain
AN6175K
14
In the standard condition, the MF signal gain, G(MF), is equal to the line output gain, that is, 21 dB. To adjust the MF signal gain,
use a proper resistor combination as indicated in a dotted box in Fig. 4–1.
Fig. 4–1 shows how the MF signal flows.
The block diagram of the receiver system in the HF mode is shown below.
There are two settings for the HF mode receiver system as follows :
Setting of the receiver preamplifier gain is the same as that in the HS mode. How to set the loudspeaker amplifier gain is described
The loudspeaker amplifier gain, G
In the standard condition, R28=R29=20 k , C26=100 pF, and C27=47 F.
Set the gain of the receiver preamplifier.
Set the gain of the loudspeaker amplifier.
BN
Vr
R32
MFI
G
(SP)
30
=20log
C32
C31
RPI
C35
(SP)
R31
AN6175K
R28// {1/(2 f C26)}
R29+ {1/(2 f C27)}
Fig.3–2 HF Mode Receiver System Block Diagram
35
, is calculated as follows :
29
To LOG4amp.
RPO
RATT
Fig.4–1 MF Signal Flow
R25
TAPC
18
19
Note : 6 dB is added for the purpose of BTL configuration.
APC
C29
R24
V
SP Pre.
+6
CC
AN6175K
1
27
(dB)
R31
2k
Vr
C28
SPI
+
–
20k
C27
38
R29
TRE
26
FB
Q3
R34
C42
R28
C26
–
+
C24
V
CC
25
1
Z
Loudspeaker
L
C25
SPO1
600
V
L
24
ICs for Telephone
C23
SPO2
+
–
Vr