FAN4274_12 Datasheet, PDF (8/13 Pages) Fairchild Semiconductor – Single and Dual, Ultra-Low Cost, Rail-to-Rail I/O, CMOS Amplifier

Application Information
General Description
The FAN4174 amplifier includes single-supply, general-
purpose, voltage-feedback amplifiers, fabricated on a bi-
CMOS process. The family features a rail-to-rail input
and output and is unity gain stable. The typical non-
inverting circuit schematic is shown in Figure 21.
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 range is exceeded. The FAN4174
typically recovers in less than 500ns from an overdrive
condition. Figure 23 shows the FAN4174 amplifier in an
overdriven condition.
Figure 21. Typical Non-inverting Configuration
Input Common Mode Voltage
The common mode input range extends to 300mV
below ground and to 100mV above V_S in single supply
operation. Exceeding these values does not cause
phase reversal; however, if the input voltage exceeds
the rails by more than 0.5V, the input ESD devices
begin to conduct. The output stays at the rail during this
overdrive condition. If the absolute maximum input V_IN
(700mV beyond either rail) is exceeded, externally limit
the input current to ±5mA, as shown in Figure 22.
Figure 23. Overdrive Recovery
Driving Capacitive Loads
Figure 9 illustrates the response of the FAN4174
amplifier family. A small series resistance (R_S) at the
output of the amplifier, illustrated in Figure 24, improves
stability and settling performance. R_S values in Figure 9
were chosen to achieve maximum bandwidth with less
than 2dB of peaking. For maximum flatness, use a
larger R_S. Capacitive loads larger than 500pF require
the use of R_S.
Figure 22. Circuit for Input Current Protection
Power Dissipation
The maximum internal power dissipation allowed is
directly related to the maximum junction temperature. If
the maximum junction temperature exceeds 150°C,
performance degradation occurs. If the maximum
junction temperature exceeds 150°C for an extended
time, device failure may occur.
Figure 24. Typical Topology for Driving a
Capacitive Load
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
FAN4174 amplifier family requires a 300series
resistor to drive a 100pF load.
© 2004 Fairchild Semiconductor Corporation
FAN4174/FAN4274 • Rev. 1.0.8
8
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