MCP609-I/SL View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'MCP609-I/SL' PDF : 42 Pages View PDF
MCP606/7/8/9
4.7.4
THREE OP AMP
INSTRUMENTATION AMPLIFIER
A classic, three op amp instrumentation amplifier is
illustrated in Figure 4-9. The two input op amps provide
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 single
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.
VO U T
=
⎛
(V1 – V2)⎝⎜1 +
-2---R----2-
RG
⎞
⎟
⎠
⎛
⎜
⎝
R-R---43-⎠⎟⎞
+ VREF
½
V2
MCP607
R3
R4
R2
VOUT
RG
R2
MCP606
R3
R4
VREF
V1
½
MCP607
FIGURE 4-9:
Three op amp
Instrumentation Amplifier.
4.7.5
PRECISION GAIN WITH GOOD
LOAD ISOLATION
In Figure 4-10, 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.
VOUT = VIN(1 + R2 ⁄ R1 )
VIN
MCP606
MCP601
VOUT
R1
FIGURE 4-10:
Load Isolation.
R2
Precision Gain with Good
DS11177D-page 14
© 2005 Microchip Technology Inc.
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