Datasheet

LM6132

SNOS751D –APRIL 2000–REVISED FEBRUARY 2013

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Typical Applications

3 OP AMP INSTRUMENTATION AMP WITH RAIL-TO-RAIL INPUT AND OUTPUT

Using the LM6134, 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 LM6134, all of these problems are eliminated.

In this example, amplifiers A and B act as buffers to the differential stage (Figure 37). These buffers assure that

the input impedance is over 100 MΩ 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.

Figure 37.

FLAT PANEL DISPLAY BUFFERING

Three features of the LM6132/34 make it a superb choice for TFT LCD applications. First, its low current draw

(360 μA per amplifier @ 5V) makes it an ideal choice for battery powered applications such as in laptop

computers. Second, since the device operates down to 2.7V, it is a natural choice for next generation 3V TFT

panels. Last, but not least, the large capacitive drive capability of the LM6132 comes in very handy in driving

highly capacitive loads that are characteristic of LCD display drivers.

The large capacitive drive capability of the LM6132/34 allows it to be used as buffers for the gamma correction

reference voltage inputs of resistor-DAC type column (Source) drivers in TFT LCD panels. This amplifier is also

useful for buffering only the center reference voltage input of Capacitor-DAC type column (Source) drivers such

as the LMC750X series.

Since for VGA and SVGA displays, the buffered voltages must settle within approximately 4 μs, the well known

technique of using a small isolation resistor in series with the amplifier's output very effectively dampens the

ringing at the output.

With its wide supply voltage range of 2.7V to 24V), the LM6132/34 can be used for a diverse range of

applications. The system designer is thus able to choose a single device type that serves many sub-circuits in

the system, eliminating the need to specify multiple devices in the bill of materials. Along with its sister parts, the

LM6142 and LM6152 that have the same wide supply voltage capability, choice of the LM6132 in a design

eliminates the need to search for multiple sources for new designs.

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