KM4470 Просмотр технического описания (PDF) - Fairchild Semiconductor
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KM4470 Datasheet PDF : 16 Pages
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KM4170, KM4270, KM4470
DATA SHEET
Application Information
General Description
The KM4X70 family of amplifiers are single supply, general
purpose, voltage-feedback amplifiers. They are fabricated on
a complementary bipolar process, feature a rail-to-rail input
and output, and are unity gain stable.
The typical non-inverting circuit schematic is shown in Figure 1.
+Vs
6.8µF
+
R11
In
R12
R2
+
0.01µF
KM4100
-
Rf
Out
Rout
Rg
Figure 1: Typical Non-inverting Configuration
Input Common Mode Voltage
The common mode input range extends to 250mV below
ground and to 250mV above Vs, in single supply operation.
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.
-
Vo
Vin
+
10kΩ
Figure 2: 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, some performance
degradation will occur. If 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 KM4X70 will typically recover
in less than 50ns from an overdrive condition. Figure 3 shows
the KM4X70 amplifier family in an overdriven condition.
G=5
Output
Input
Time (10µs/div)
Figure 3: Overdrive Recovery
Driving Capacitive Loads
The Frequency Response vs. CL plot, illustrates the response
of the KM4X70 amplifier family. A small series resistance
(Rs) at the output of the amplifier, illustrated in Figure 4, will
improve stability and settling performance. Rs values in the
Frequency Response vs. CL plot were chosen to achieve maximum
bandwidth with less than 2dB of peaking. For maximum
flatness, use a larger Rs. Capacitive loads larger than 50pF
require the use of Rs.
+
-
Rf
Rg
Rs
CL RL
Figure 4: 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 KM4X70 amplifier
family requires a 510Ω series resistor to drive a 100pF load.
REV. 5 December 2002
7
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