KA3032
5. FOCUS, TRACKING ACTUATOR, APINDLE, SLED MOTOR DRIVE PART
M
Rfeed2
Rfeed2
AP2
-
AP3
+
−
Vr
IC
Rref2
Rref2
+
−
SHIFT
LEVEL
Rfeed1
AP1
−
+
46
−
Rref1
Vref
1
4
3
9
8
12
11
BF
−
48
Vin
2
5 10 47
• The voltage, Vref is the reference voltage given by the external bias voltage of pin 46.
• The input signal (Vin) through pin 2, 5, 10 and 47 are by the AP1 amplified one times (Rref1=Rfeed1) and then fed to the
level shift.
• The level shift produces the current due to the difference between the input signal and the arbitrary reference signal. The
current produced as +∆I and −∆I are fed into the output amplifier. Where output amplifier (AP2, 3) gain is two times (all
Rref2 = Rfeed2).
• If you desire to change the gain, the input buffer amplifier (BF) can be used.
• The output stage is the balanced transformerless (BTL) driver.
• The bias voltage Vr is expressed as below;
V
CC – VBE
---------------------------
Vr =
[V]
2
15
FAIRCHILD [ FAIRCHILD SEMICONDUCTOR ]
