AN618 Panasonic Semiconductor, AN618 Datasheet - Page 11

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

ICs for Telephone
The external components, R12, R13, C6, and C45, determine the MIC preamplifier gain/frequency characteristics in the HS mode
as shown in Fig. 2—2. R12 and C6 form a low-pass filter, and R13 and C45 form a high-pass filter.
Referring to the above calculations :
The HS mode transmitter frequency characteristics are calculated as follows :
MIC Preamplifier Gain/Frequency Characteristics Adjustment
V
CC
MAI
1
R14
• High-band cutoff frequency, f
• Low-band cutoff frequency, f
• For the high-pass filter, the larger the C45 capacitance, the lower the cutoff frequency, or the smaller the capacitance, the
• For the low-pass filter, the larger the C6 capacitance, the lower the cutoff frequency, or the smaller the capacitance, the
higher the frequency.
higher the frequency. See Fig.2—3.
ECM
Fig.2—2 MIC Preamplifier
3
Vr
R13
C45
+
–
R12
C6
AN6175K
4
Fig.2—3 HS Mode Transmitter Frequency Characteristics
To APC
MAO
LC
HC
Larger C45
=1/(2 C45 · R13)
=1/(2 C6 · R12)
Standard C45
300
Smaller C45 Larger C6
Input Frequency (Hz)
Referring to Fig.2—2, the MIC preamplifier gain, G
culated as follows :
G
In the standard condition, R12=R13=10 k , C6=102 pF, and C45
= 0.1 F.
(HSMIC)
1k
= 20log
4k
Standard C6
{1/ (2 f C45)} + R13 (dB)
{1/ (2 f C6)}// R12
Smaller C6
(HSMIC)
AN6175K
, is cal-
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