35.3.7 Application Usage

The OPAMP peripheral is highly flexible and can be used in various analog signal conditioning applications. This section describes a broad range of configurations and the multiplexer settings required to achieve them. Many of these configurations require no external components.

Figure 35-2. Op Amp Connected Directly to Pins
The figure above displays an op amp connected directly to the pins of the device without being connected to any of the internal resistors. This is useful for situations where the user desires to make all connections to other components externally. The multiplexer settings required to achieve this configuration are:
Table 35-3. Op Amp Connected Directly to Pins
OPnINMUXOPnRESMUX
MUXPOSMUXNEGMUXBOTMUXWIPMUXTOP
OPnINP INN OFFWIP0OFF

Figure 35-3. Voltage Follower
The figure above displays a voltage follower, also known as a unity-gain buffer. The non-inverting (+) input is connected to a pin, and the output is connected to the inverting (-) input. The multiplexer settings required for this configuration are:
Table 35-4. Voltage Follower
OPnINMUXOPnRESMUX
MUXPOSMUXNEGMUXBOTMUXWIPMUXTOP
OPnINPOUT OFFWIP0OFF

Figure 35-4. Non-Inverting PGA
The figure above displays a non-inverting Programmable Gain Amplifier. The required multiplexer settings are as follows:
Table 35-5. Non-Inverting PGA
OPnINMUXOPnRESMUX
MUXPOSMUXNEGMUXBOTMUXWIPMUXTOP
OPnINP WIP GND Setting determines gainOUT

Figure 35-5. Inverting PGA
The figure above shows the inverting PGA configuration. The multiplexer settings required are:
Table 35-6. Inverting PGA
OPnINMUXOPnRESMUX
MUXPOSMUXNEGMUXBOTMUXWIPMUXTOP
OPnVDDDIV2WIP INN Setting determines gainOUT

Figure 35-6. Integrator
The figure above shows how an op amp can be configured as an integrator. An external capacitor and external resistor are required. The DUMPn event closes a switch to discharge the capacitor and reset the integrator. The multiplexer settings required are:
Table 35-7. Integrator
OPnINMUXOPnRESMUX
MUXPOSMUXNEGMUXBOTMUXWIPMUXTOP
OPnVDDDIV2 INN OFFWIP0OFF

Figure 35-7. Differential Amplifier using Two Op Amps
The figure above shows how a differential amplifier can be constructed from two op amps. The differential amplifier accepts two input signals, V1 and V2. The output also consists of two signals, OP1OUT and V2. The difference of the output signals, VDIFF, is proportional to the difference (V2-V1) of the two input signals. The multiplexer settings required to implement this configuration are as follows:
Table 35-8. Differential Amplifier using Two Op Amps
OPnINMUXOPnRESMUX
MUXPOSMUXNEGMUXBOTMUXWIPMUXTOP
OP0INP OUT OFFWIP0OFF
OP1INP WIP LINKOUT (OP0OUT) Setting determines gainOUT

Figure 35-8. Cascaded (Two) Non-Inverting PGA
The figure above shows a cascaded non-inverting PGA constructed from two op amps. The following multiplexer settings are required:
Table 35-9. Cascaded (Two) Non-Inverting PGA
OPnINMUXOPnRESMUX
MUXPOSMUXNEGMUXBOTMUXWIPMUXTOP
OP0INP WIP GND Determines gainOUT
OP1LINKOUT (OP0OUT)WIPGND Determines gainOUT

Figure 35-9. Cascaded (Two) Inverting PGA
The figure above shows a cascaded inverting PGA constructed from two op amps. The required multiplexer settings are:
Table 35-10. Cascaded (Two) Inverting PGA
OPnINMUXOPnRESMUX
MUXPOSMUXNEGMUXBOTMUXWIPMUXTOP
OP0VDDDIV2 WIP INN Determines gainOUT
OP1VDDDIV2 WIPLINKOUT (OP0OUT) Determines gainOUT

Figure 35-10. Cascaded (Three) Non-Inverting PGA
The figure above shows a cascaded non-inverting PGA constructed from three op amps. The following multiplexer settings are required:
Table 35-11. Cascaded (Three) Non-Inverting PGA
OPnINMUXOPnRESMUX
MUXPOSMUXNEGMUXBOTMUXWIPMUXTOP
OP0INP WIP GND Determines gainOUT
OP1LINKOUT (OP0OUT)WIPGND Determines gainOUT
OP2LINKOUT (OP1OUT) WIP GND Determines gainOUT

Figure 35-11. Cascaded (Three) Inverting PGA
The figure above shows a cascaded inverting PGA constructed from three op amps. The required multiplexer settings are:
Table 35-12. Cascaded (Three) Inverting PGA
OPnINMUXOPnRESMUX
MUXPOSMUXNEGMUXBOTMUXWIPMUXTOP
OP0VDDDIV2 WIP INN Determines gainOUT
OP1VDDDIV2 WIPLINKOUT (OP0OUT) Determines gainOUT
OP2VDDDIV2WIP LINKOUT (OP1OUT) Determines gainOUT

Figure 35-12. Instrumentation Amplifier
The figure above displays three op amps configured as an instrumentation amplifier. The following multiplexer settings are required:
Table 35-13. Instrumentation Amplifier
OPnINMUXOPnRESMUX
MUXPOSMUXNEGMUXBOTMUXWIPMUXTOP
OP0INP OUT GND See the table belowOUT
OP1INP OUT OFFWIP0OFF
OP2LINKWIP (OP0WIP) WIP LINKOUT (OP1OUT)See the table belowOUT
Configure the resistor ladders associated with OP0 and OP2 as follows to select the desired gain:
Table 35-14. Gain Selection for Instrumentation Amplifier
GAINOP0RESMUX.MUXWIPOP2RESMUX.MUXWIP
1/150x70x0
1/70x60x1
1/30x50x2
10x30x3
30x20x5
70x10x6
150x00x7