km4211 Fairchild Semiconductor, km4211 Datasheet - Page 6

• Manufacturer Part Number: km4211
• Description: Dual, 0.2ma, Low Cost, 2.7v & 5v, 35mhz Rail-to-rail Amp
• Manufacturer: Fairchild Semiconductor

DATA SHEET
General Description
The KM4211 is a single supply, general purpose, voltage-
feedback amplifier fabricated on a complementary
bipolar process. The KM4211 offers 35MHz unity gain
bandwidth, 27V/µs slew rate, and only 208µA supply
current. It features a rail-to-rail output stage and is
unity gain stable.
The design utilizes a patent pending topology that
provides increased slew rate performance. The common
mode input range extends to 300mV below ground
and to 1.2V below V s . 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.
The design uses a Darlington output stage. The out-
put stage is short circuit protected and offers “soft”
saturation protection that improves recovery time.
The typical circuit schematic is shown in Figure 1.
Enable/Disable Function (KM4121)
The KM4121 offers an active-low disable pin that can
be used to lower its supply current. Leave the pin
floating to enable the part. Pull the disable pin to the
negative supply (which is ground in a single supply
application) to disable the output. During the disable
condition, the nominal supply current will drop to
below 40µA and the output will be at high impedance
with about 2pF capacitance.
Power Dissipation
The maximum internal power dissipation allowed is
directly related to the maximum junction tempera-
ture. If the maximum junction temperature exceeds
150°C, some reliability degradation will occur. If the
maximum junction temperature exceeds 175°C for an
extended time, device failure may occur.
6
In
Figure 1: Typical Configuration
R
g
KM4211
+
-
+V
s
0.01µF
6.8µF
+
R
f
Out
The KM4211 is short circuit protected. However, this
may not guarantee that the maximum junction
temperature (+150°C) is not exceeded under all
conditions. Follow the maximum power derating
curves shown in Figure 2 to ensure proper operation.
Overdrive Recovery
For an amplifier, an overdrive condition 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 KM4211 will typically recover in less
than 20ns from an overdrive condition. Figure 3 shows
the KM4111 in an overdriven condition.
Driving Capacitive Loads
A small series resistance (R
amplifier, illustrated in Figure 4, will improve stability
and settling performance.
2.0
1.5
1.0
0.5
0
Figure 2: Power Derating Curves
-50
Maximum Power Dissipation
Figure 3: Overdrive Recovery
Input
-30
MSOP-8 lead
Ambient Temperature ( C)
-10
Output
SOIC-8 lead
Time (1µs/div)
10
s
30
) at the output of the
50
70
REV. 1 June 2001
90
KM4211