FAN4272 Fairchild Semiconductor, FAN4272 Datasheet - Page 7

• Manufacturer Part Number: FAN4272
• Description: Dual/ Low Cost/ +2.7V & +5V/ Rail-to-Rail I/O Amplifier
• Manufacturer: Fairchild Semiconductor

FAN4272
Rev. 2 December 2002
Application Information
General Description
The FAN4272 is single supply, general purpose, voltage-feed-
back amplifier. The FAN4272 is fabricated on a complementary
bipolar process, features a rail-to-rail input and output, and is
unity gain stable.
The typical non-inverting circuit schematic is shown in Figure 1.
Input Common Mode Voltage
The common mode input range extends to 250mV below
ground and to 250mV above V
Exceeding these values will not cause phase reversal. However,
if the input voltage exceeds the rails by more than 0.5V, the
input ESD devices will begin to conduct. The output will
stay at the rail during this overdrive condition. If the absolute
maximum input voltage (700mV beyond either rail) is
exceeded, externally limit the input current to ±5mA as shown
in Figure 2.
Power Dissipation
The maximum internal power dissipation allowed is directly
related to the maximum junction temperature. If the maximum
junction temperature exceeds 150°C, some performance
Figure 1: Typical Non-inverting Configuration
Figure 2: Circuit for Input Current Protection
V
in
In
10kΩ
R
g
FAN4272
-
+
+V
FAN4272
+
-
s
0.01µF
s
6.8µF
, in single supply operation.
+
R
f
Out
V
o
degradation will occur. It the maximum junction temperature
exceeds 175°C for an extended time, device failure may occur.
Overdrive Recovery
Overdrive of an amplifier occurs when the output and/or
input ranges are exceeded. The recovery time varies based on
whether the input or output is overdriven and by how much
the ranges are exceeded. The FAN4272 will typically recover
in less than 50ns from an overdrive condition. Figure 3
shows the FAN4272 in an overdriven condition.
Driving Capacitive Loads
The Frequency Response vs. C
of the FAN4272. A small series resistance (R
of the amplifier, illustrated in Figure 4, will improve stability
and settling performance. R
vs. C
less than 2dB of peaking. For maximum flatness, use a larger
R
Driving a capacitive load introduces phase-lag into the output
signal, which reduces phase margin in the amplifier. The
unity gain follower is the most sensitive configuration. In a
unity gain follower configuration, the FAN4272 requires a
75 series resistor to drive a 100pF load.
s
. Capacitive loads larger than 200pF require the use of R
L
plot were chosen to achieve maximum bandwidth with
Figure 4: Typical Topology for driving
-0.5
5.5
4.5
3.5
2.5
1.5
0.5
R
Figure 3: Overdrive Recovery
g
0
G = 5
-
+
10
a capacitive load
20
R
s
f
30
values in the Frequency Response
Time (µs)
Output
Input
L
40
plot, illustrates the response
R
50
s
60
C
s
70
) at the output
L
DATA SHEET
80
R
L
s
7
.