ml4833 Microsemi Corporation, ml4833 Datasheet - Page 7

• Manufacturer Part Number: ml4833
• Description: Electronic Dimming Ballast Controller
• Manufacturer: Microsemi Corporation

TRANSCONDUCTANCE AMPLIFIERS
The PFC voltage feedback amplifier is implemented as an
operational transconductance amplifier. It is designed to
have low small signal forward transconductance such that
a large value of load resistor (R1) and a low value
ceramic capacitor (<1µF) can be used for AC coupling
(C1) in the frequency compensation network. The
compensation network shown in Figure 3 will introduce a
zero and a pole at:
PFC OUT
CLK
RAMP
FILTER
f
EMI
Z
SINE
2
R C
1
1 1
2
f
P
PIFB
–A
2
R C
1
1 2
Figure 2. ML4833 PFC Controller Section
R
L
SENSE
SINE
10
C
OUT A
RAMP
C
RAMP
+
–
14
(2)
OSC
V TO I
SW1
R1
C1
SW2
1
S
R
PEAO
PEAO
Q
PVFB/OVP
2.5V
CLK
18
Figure 3. Compensation Network
C2
–
+
–
+
RA
RB
VREF1
V
OUT
INVERTER
C1
R1
18
NETWORK
PVFB/OVP
LAMP
ML4833
C2
M
M
L
A
P
L
A
P
7