BA3121N Rohm Semiconductor, BA3121N Datasheet - Page 5

• Manufacturer Part Number: BA3121N
• Description: IC AMP AUDIO STER AB 8SIP
• Manufacturer: Rohm Semiconductor
• Type: Class ABr

Specifications of BA3121N

• Output Type: 2-Channel (Stereo)
• Voltage - Supply: 4 V ~ 18 V
• Mounting Type: Through Hole
• Package / Case: 8-SIP
• Product: General Purpose Audio Amplifiers
• Common Mode Rejection Ratio (min): 57 dB
• Thd Plus Noise: 0.002 %
• Operating Supply Voltage: 12 V
• Supply Current: 9 mA
• Maximum Power Dissipation: 900 mW
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• Minimum Operating Temperature: - 30 C
• Supply Voltage (max): 18 V
• Supply Voltage (min): 4 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Max Output Power X Channels @ Load: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

FCircuit operation
Car-audio systems are earthed to the car body, and for
this reason, electrical noise generated by the car elec-
trics can enter the power amplifier input via the chassis,
and become audible.
The BA3121 makes use of the common-mode rejection
characteristics of an operational amplifier to eliminate
this noise. Without the BA3121 noise enters the power
amplifier input directly, when used, the CMMR of opera-
tional amplifiers 1-A and 2-A eliminates the noise.
Principles of noise elimination:
To obtain the output voltage (e
From
Ideally, if R
become zero. However, due to mismatching between the
resistors, difference in the noise voltages (e
tolerances in the operational amplifier, a noise voltage
does result.
Audio ICs
V
e
e
e
1
O
O
O
i
=
and
= *
= *
= *
1
R
(R
4
2
R
R
R
R
R
R
= R
3
R
)R
2
1
2
1
2
1
4
2
e
e
R
S (e
4
1
1
)
3
)
)
, and e
1
*e
S e
R
R
1
2
1
)R
R
2
) )
)R
R
1
1
= e
1
O
2
)
2
2
, the noise voltage will
S
R
R
1
S V
1
(R
R
(R
4
3
*R
i
R
)R
3
)R
4
1
1
2
and e
2
4
R
)
4
)
3
S e
2
S e
), and
2
2
With the BA3121, the elimination level of the noise is ex-
pressed as: CMMR = 20log (e
Therefore, CMRR y 41dB can be guaranteed.
FOperation notes
(1)
tors connected to pin 2 (V
ripple rejection ratio stable. If this ratio is maintained, the
ripple rejection ratio will not vary significantly even if the
capacitance values are halved.
(2)
in the example is doubled, the bass-region CMMR will be
+6dB, and if it is halved, it will be *6dB (see Fig. 16).
Maintain a ratio of 2: 1 for the values of the capaci-
If the value of the capacitor connected to pin 2 (V
BA3121 / BA3121F / BA3121N
m1
) and pin 6 (V
O
/ e
i
) (e
i
= e
m2
1
) to keep the
= e
2
)
721
m1
)