Datasheet
2009-2011 Microchip Technology Inc. DS22197B-page 25
MCP631/2/3/4/5/9
Keep sensitive traces short and straight. Separate
them from interfering components and traces. This is
especially important for high frequency (low rise time)
signals.
Sometimes, it helps to place guard traces next to victim
traces. They should be on both sides of the victim
trace, and as close as possible. Connect guard traces
to ground plane at both ends, and in the middle for long
traces.
Use coax cables, or low inductance wiring, to route
signal and power to and from the PCB. Mutual and self
inductance of power wires is often a cause of crosstalk
and unusual behavior.
4.7 Typical Applications
4.7.1 POWER DRIVER WITH HIGH GAIN
Figure 4-10 shows a power driver with high gain
(1 + R
2
/R
1
). The MCP631/2/3/4/5/9 op amp’s short cir-
cuit current makes it possible to drive significant loads.
The calibrated input offset voltage supports accurate
response at high gains. R
3
should be small, and equal
to R
1
||R
2
, in order to minimize the bias current induced
offset.
FIGURE 4-10: Power Driver.
4.7.2 OPTICAL DETECTOR AMPLIFIER
Figure 4-11 shows a trans-impedance amplifier, using
the MCP63X op amp, in a photo detector circuit. The
photo detector is a capacitive current source.
R
F
provides enough gain to produce 10 mV at V
OUT
.
C
F
stabilizes the gain and limits the trans-impedance
bandwidth to about 1.1 MHz. R
F
’s parasitic
capacitance (e.g., 0.2 pF for a 0805 SMD) acts in
parallel with C
F
.
FIGURE 4-11: Trans-impedance Amplifier
for an Optical Detector.
4.7.3 H-BRIDGE DRIVER
Figure 4-12 shows the MCP632 dual op amp used as
a H-bridge driver. The load could be a speaker or a DC
motor.
FIGURE 4-12: H-Bridge Driver.
This circuit automatically makes the noise gains (G
N
)
equal, when the gains are set properly, so that the
frequency responses match well (in magnitude and in
phase). Equation 4-7 shows how to calculate R
GT
and
R
GB
so that both op amps have the same DC gains;
G
DM
needs to be selected first.
EQUATION 4-7:
Equation 4-8 gives the resulting common mode and
differential mode output voltages.
EQUATION 4-8:
R
1
R
2
V
IN
V
DD
/2
V
OUT
R
3
R
L
MCP63X
Photo
Detector
C
D
C
F
R
F
V
DD
/2
30pF
100 k
1.5 pF
I
D
100 nA
V
OUT
MCP63X
R
F
R
F
V
IN
V
OT
R
F
R
GB
V
OB
V
DD
/2
R
GT
R
L
½ MCP632
½ MCP632
G
DM
V
OT
V
OB
–
V
IN
V
DD
2
–
-------------------------------- 1 V / V
R
GT
R
F
G
DM
2
1–
---------------------------------=
R
GB
R
F
G
DM
2
-------------------=
V
OT
V+
OB
2
---------------------------
V
DD
2
-----------=
V
OT
V–
OB
G
DM
V
IN
V
DD
2
-----------–
=