Datasheet

 2011-2013 Microchip Technology Inc. DS70000657H-page 359
dsPIC33EPXXXGP50X, dsPIC33EPXXXMC20X/50X AND PIC24EPXXXGP/MC20X
25.1.2 OP AMP CONFIGURATION B
Figure 25-7 shows a typical inverting amplifier circuit
with the output of the op amp (OAxOUT) externally
routed to a separate analog input pin (ANy) on the
device. This op amp configuration is slightly different in
terms of the op amp output and the ADC input
connection, therefore, R
INT1 is not included in the
transfer function. However, this configuration requires
the designer to externally route the op amp output
(OAxOUT) to another analog input pin (ANy). See
Table 30-53 in Section 30.0 “Electrical Characteris-
tics” for the typical value of R
INT1. Table 30-60 and
Table 30-61 in Section 30.0 “Electrical Characteris-
tics” describe the minimum sample time (TSAMP)
requirements for the ADC module in this configuration.
Figure 25-7 also defines the equation to be used to
calculate the expected voltage at point V
OAXOUT. This
is the typical inverting amplifier equation.
25.2 Op Amp/Comparator Resources
Many useful resources are provided on the main prod-
uct page of the Microchip web site for the devices listed
in this data sheet. This product page, which can be
accessed using this link, contains the latest updates
and additional information.
25.2.1 KEY RESOURCES
• “Op Amp/Comparator” (DS70357) in the
“dsPIC33/PIC24 Family Reference Manual”
• Code Samples
• Application Notes
• Software Libraries
• Webinars
• All Related “dsPIC33/PIC24 Family Reference
Manual” Sections
• Development Tools
FIGURE 25-7: OP AMP CONFIGURATION B
Note: In the event you are not able to access the
product page using the link above, enter
this URL in your browser:
http://www.microchip.com/wwwproducts/
Devices.aspx?dDocName=en555464
ADC
(3)
OAxOUT
RFEEDBACK
(2)
ANy
Note 1: See Table 30-53 for the Typical value.
2: See Table 30-53 for the Minimum value for the feedback resistor.
3: See Table 30-60 and Table 30-61 for the minimum sample time (T
SAMP).
4: CV
REF1O or CVREF2O are two options that are available for supplying bias voltage to the op amps.
–
+
Op Ampx
(VOAXOUT)
RINT1
(1)
V
OAxOUT
R
FEEDBACK
R
1
------------------------------


Bias Voltage V–
IN
=
CxIN1-
CxIN1+
R
1
VIN
Bias
Voltage
(4)