336

Optical disc ICs

BA6397FP

FCircuit 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

corresponding to the input voltage. This current is

passed through a resistor and into the internal reference

voltage component, the preamplifier output being a sig-

nal centering on the internal reference voltage. Two sys-

tems (positive phase and negative phase) are created

during V / I conversion, generating BTL output via the

driver buffer.