LM6142, LM6144
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SNOS726D –JUNE 2000–REVISED MARCH 2013
Figure 39.
Figure 40.
Typical Applications
FISH FINDER/ DEPTH SOUNDER.
The LM6142/LM6144 is an excellent choice for battery operated fish finders. The low supply current, high gain-
bandwidth and full rail to rail output swing of the LM6142 provides an ideal combination for use in this and similar
applications.
ANALOG TO DIGITAL CONVERTER BUFFER
The high capacitive load driving ability, rail-to-rail input and output range with the excellent CMR of 82 dB, make
the LM6142/LM6144 a good choice for buffering the inputs of A to D converters.
3 OP AMP INSTRUMENTATION AMP WITH RAIL-TO-RAIL INPUT AND OUTPUT
Using the LM6144, a 3 op amp instrumentation amplifier with rail-to-rail inputs and rail to rail output can be made.
These features make these instrumentation amplifiers ideal for single supply systems.
Some manufacturers use a precision voltage divider array of 5 resistors to divide the common-mode voltage to
get an input range of rail-to-rail or greater. The problem with this method is that it also divides the signal, so to
even get unity gain, the amplifier must be run at high closed loop gains. This raises the noise and drift by the
internal gain factor and lowers the input impedance. Any mismatch in these precision resistors reduces the CMR
as well. Using the LM6144, all of these problems are eliminated.
In this example, amplifiers A and B act as buffers to the differential stage (Figure 41). These buffers assure that
the input impedance is over 100MΩ and they eliminate the requirement for precision matched resistors in the
input stage. They also assure that the difference amp is driven from a voltage source. This is necessary to
maintain the CMR set by the matching of R1–R2 with R3–R4.
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