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2022-09-19 17:33:03
BA3121 / BA3121F / BA3121N is a grounded isolation amplifier
Description
BA3121 , BA3121F, and BA3121N are ground isolation amplifiers developed for car audio applications. These integrated circuits effectively eliminate the problems caused by wiring resistance and the noise generated by automotive electrical equipment. The capacitor value of the external capacitors required for integrated circuits is small, allowing compact and reliable settings.
Application
Auto audio system
Features
1), no large capacitor
2), high -co -model suppression ratio (57db typical values. F 1kHz).
3), low noise (vno 3.5 μVRMS typical value).
4), low inconsistency (THD 0.002%typical value).
5), two channels.
Absolute maximum rated value (TA 25C)
Circuit operation
Circuit operation 
BA3121 uses the co -mode suppression characteristics of the computing amplifier to eliminate this noise. In the case of no BA3121 noise entering the power amplifier input, the operating amplifier 1-a and 2-A CMMR eliminates the noise when using it.
Principles of Voice:
Obtaining output voltage (EO)
From 1 and 2
Ideally, if R1R4 R2R3, E1 E2, the noise voltage will become zero. However, due to non -matching between resistors, differences in noise voltage (E1 and E2), and the tolerance of the computing amplifier, noise voltage will indeed produce.
Use BA3121, and the level of noise elimination is expressed as: cmmr 20log (eo/ei) (ei e1 E2), so CMRR 41DB can be guaranteed.
Operation description
(1), the capacitor value connected to the pink 2 (VM1) and pin 6 (VM2) maintains a ratio of 2: 1. Essence If this ratio is maintained, even if the capacitance value is halved, the ripple suppression rate will not change significantly.
(2)If the capacitance value connected to the pin 2 (VM1) in the sample doubles, the bass area CMMR will be+6DB, and if half is reduced, it is 6DB (see Figure 16).
Application instance
Electrical characteristic curve 
appearance size (unit: mm)
