Datasheet

MCP6071/2/4
DS22142B-page 18 © 2010 Microchip Technology Inc.
4.7 Application Circuits
4.7.1 GYRATOR
The MCP6071/2/4 op amps can be used in gyrator
applications. The gyrator is an electric circuit which can
make a capacitive circuit behave inductively.
Figure 4-8 shows an example of a gyrator simulating
inductance, with an approximately equivalent circuit
below. The two Z
IN
have similar values in typical
applications. The primary application for a gyrator is to
reduce the size and cost of a system by removing the
need for bulky, heavy and expensive inductors. For
example, RLC bandpass filter characteristics can be
realized with capacitors, resistors and operational
amplifiers without using inductors. Moreover, gyrators
will typically have higher accuracy than real inductors,
due to the lower cost of precision capacitors than
inductors.
.
FIGURE 4-8: Gyrator.
4.7.2 INSTRUMENTATION AMPLIFIER
The MCP6071/2/4 op amps are well suited for
conditioning sensor signals in battery-powered
applications. Figure 4-9 shows a two op amp
instrumentation amplifier, using the MCP6072, that
works well for applications requiring rejection of
common mode noise at higher gains. The reference
voltage (V
REF
) is supplied by a low impedance source.
In single supply applications, V
REF
is typically V
DD
/2.
FIGURE 4-9: Two Op Amp
Instrumentation Amplifier.
To obtain the best CMRR possible, and not limit the
performance by the resistor tolerances, set a high gain
with the R
G
resistor.
4.7.3 PRECISION COMPARATOR
Use high gain before a comparator to improve the
latter’s input offset performance. Figure 4-10 shows a
gain of 11 V/V placed before a comparator. The
reference voltage V
REF
can be any value between the
supply rails.
FIGURE 4-10: Precision, Non-inverting
Comparator.
MCP6071
R
L
V
OUT
Gyrator
Z
IN
R
C
Z
IN
R
L
jωL+=
LR
L
RC=
R
L
L
Z
IN
Equivalent Circuit
V
OUT
V
1
V
2
–()1
R
1
R
2
----- -
2R
1
R
G
---------++
⎝⎠
⎛⎞
V
REF
+=
V
REF
R
1
R
2
R
2
R
1
V
OUT
R
G
V
2
V
1
½
MCP6072
½
MCP6072
V
IN
1MΩ
V
OUT
MCP6071
100 kΩ
MCP6541
V
REF