2. About the built-in operational ampliﬁers
The LA8608V has three independent operational ampliﬁers on chip that can be used as needed. If they are not to be used, short
the I/O pins.
Sample application 1: Noise ampliﬁer
Using the three operational ampliﬁers, it is possible to form a secondary biquad bandpass ﬁlter. (For details on the ﬁlter
response characteristics, refer to the data provided later.)
The calculation of the transfer function for the above diagram is as shown below.
In normal use, R3 = R4 = R5 = R6 = Rf, and C1 = C2 = Cf:
Q = CfR2 x ω0
H = R2Rf
fo = center frequency, H = pass band gain, Q = selectivity
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