AN618 Panasonic Semiconductor, AN618 Datasheet - Page 12

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

AN6175K
2–2 Setting the Receiver System
12
HPF are calculated as follows(see Fig. 2-6) :
1. Receiver Preamplifier Frequency Characteristics Setting
The block diagram of the receiver system in the HS mode is shown below.
There are two adjustments for the HS mode receiver system as follows :
In the standard condition, R31=56 k , R32=220 k , and C31=C32= 0.0047 F.
Fig.2–5 is the block diagram for the receiver preamplifier.
A high-pass filter(HPF)consisting of R31, R32, C31, and C32 blocks external hum noise. The frequency characteristics of the
F
1. Set the frequency characteristics of the receiver preamplifier.
2. Adjust the receiver amplifier.
Fig.2–5 Receiver Preamplifier Block Diagram
N
Receiver preamplifier
=
BN
AN6175K
Vr
2
1
R32
30
C31 C32
BN
C32
C31
RPI
Vr
1
R32
R31
Fig.2–4 HS Mode Receiver System Block Diagram
30
29
To LOG4amp.
Receiver
preamplifier
R31 R32
To receiver amplifier
RPI
C32
C31
RPO
1
R31
20
29
To LOG4amp.
RPO
V
CC
1
R24
AN6175K
RAPC
20
R25
C20
APC
C22
–3
22
0
Receiver amplifier
Fig.2–6 HPF Frequency Characteristics
–
DO
R26
Handset receiver
21
R27
DI
Frequency (Hz)
C21
ICs for Telephone
F
N