BA7725 ROHM Electronics, BA7725 Datasheet - Page 6

• Manufacturer Part Number: BA7725
• Description: Analog Compander for Karaoke echo Systems
• Manufacturer: ROHM Electronics

•
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.
•
(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.
6
V
Multimedia ICs
Microphone amplifier frequency
characteristic measurement circuit
Measurement circuit
Circuit operation
IN
1.5k
MIC AMP IN
22
12k
Fig.2
–
+
LINE
OUT
BA7725S
C1
1
C30
2.2k
+
21
2.2
R2
+
V
22
1
out
R31
10k
82k
R3
21
+
2
R33
1k
MIC AMP IN
C20
0.1
SW
20
3
LINE
IN
LINE OUT
+
V
CC
19
V4
VR
4
9V
22
C4
+
18
5
+
+
R9
+
0.1
Fig.1
V6
C5
17
VR
COMPRESS
6
22
1
+ 18dB
R10
Fig.4
0.47
0.1
C20
+
16
C6
21
7
+
2
EXPAND
R8
SW
0.47
C19
+
15
8
+
C10
LINE IN
14
9
R11
C18
R17
BF
BF
13
10
C15
R16
– 10
– 20
– 30
– 40
60
50
40
30
20
10
0
10k
12
11
BA7725S / BA7725FS
Microphone amplifier frequency
characteristics
R13
2
C14
0.1
C32
C33
0.1
4 6 8 1
Frequency characteristic (Hz)
100k
R34
1k
R35
10k
CMP BF OUT
DLY BF IN
2
Fig.3
Open loop gain
4
6
8
1M
1
2
4
6
8
10M
1