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Optical disc ICs BA6897S/BA6897FP
Circuit operation
(1) Driver
Inputs to the IC are the focus tracking error signal from
the servo preamplifier and the control signal from the mo-
tor.
The input signals, which normally center on 2.5V, are V/I
converted by the preamplifier, generating a current corre-
sponding to the input voltage. This current is passed
through a resistor and into the internal reference voltage
component, the preamplifier output being a signal cen-
tering on the internal reference voltage. Two systems
(positive phase and negative phase) are created during
V/I conversion, generating BTL output via the driver buff-
er.
(2) Regulator
This is a typical series regulator that generates a refer-
ence voltage internally. A PNP low saturation transistor
must be connected.
(3) Amplifier
General 4558 type.
