BA7725S データシートの表示（PDF） - ROHM Semiconductor
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BA7725S Datasheet PDF : 8 Pages
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Multimedia ICs
BA7725S / BA7725FS
•Measurement circuit
MIC AMP IN
R2 R3
2.2k 82k
C1 +
1µ
22 21
VCC 9V
C5 C6
0.1µ 0.47µ
C4
22µ
+
R8 C10 R11
+
20 19 18 17 16 15 14 13
+
COMPRESS
BF
C32
0.1µ
R35
10k
CMP BF OUT
C33
12 0.1µ
DLY BF IN
R34
1k
+ SW + VR
VR
EXPAND
BF
1
2
3
4
5
6
7
8
9 10 11
C30 +
2.2µ
R31
10k
C20
0.1µ
R33
1k
+
C20 C19
0.1µ 0.47µ
R17
R13
C15
C18 R16 C14
LINE
OUT
LINE
IN
V4
V6
Fig.1
The above measurement circuit applies to a BA7725S mount-
ed to a 22-pin SDIP package. A BA7725FS mounted to a 20-
pin SSOP-A package lacks N.C. pins 3 and 20; other than this
difference, the above circuit diagram applies.
•Circuit operation
(1) MIC AMP IN / LINE OUT gain
Microphone amplifier gain (determined by R9 and R10) + line
amplifier gain (+12dB)
The audio signal is input via pin 22 (BA7725S) or pin 20
(BA7725FS) and amplified by the internal microphone amplifi-
er, whose gain can be set with (attached) R9 and R10.
Note: Microphone amplifier gain must be set above +15dB.
1.5k
12k
VIN
MIC AMP IN
Vout
R9 R10
+
22 21
22
–
+
21
BA7725S
Microphone amplifier frequency
characteristic measurement circuit
Fig.2
6
LINE OUT
+ 18dB
+ SW +
12
+
LINE IN
Fig.4
60
50
40
Open loop gain
30
20
10
0
– 10
– 20
– 30
2
– 40
10k
4 6 81 2 4 6 81 2 4 6 81
100k
1M
10M
Frequency characteristic (Hz)
Microphone amplifier frequency
characteristics
Fig.3
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