MCP609-IP datasheet(16/32 Pages) MICROCHIP

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MCP606/7/8/9

DS11177E-page 16

4.8.4

THREE OP AMP

INSTRUMENTATION AMPLIFIER

A classic, three op amp instrumentation amplifier is

illustrated in Figure 4-12. The two input op amps pro-

vide differential signal gain and a common mode gain

of +1. The output op amp is a difference amplifier,

which converts its input signal from differential to a sin-

gle ended output; it rejects common mode signals at its

input. The gain of this circuit is simply adjusted with one

resistor (RG). The reference voltage (VREF) is typically

referenced to mid-supply (VDD/2) in single-supply

applications.

FIGURE 4-12:

Three op amp

Instrumentation Amplifier.

4.8.5

PRECISION GAIN WITH GOOD

LOAD ISOLATION

In Figure 4-13, the MCP606 op amps, R1 and R2

provide a high gain to the input signal (VIN). The

MCP606’s low offset voltage makes this an accurate

circuit.

The MCP601 is configured as a unity-gain buffer. It

isolates the MCP606’s output from the load, increasing

the high-gain stage’s precision. Since the MCP601 has

a higher output current, with the two amplifiers being

housed in separate packages, there is minimal change

in the MCP606’s offset voltage due to loading effect.

FIGURE 4-13:

Precision Gain with Good

Load Isolation.

OUT

–

() 1

---------

⎝⎠

⎜⎟

⎛⎞ R

------

⎝⎠

⎜⎟

⎛⎞

REF

MCP607

VREF

MCP606

MCP607

VOUT

OUT

IN 1R2 R1

⁄

()

MCP606

VOUT

VIN

MCP601

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