A buffered-reference configuration is useful when
the source impedance is high (for example, a voltage divider). Buffering a
high-impedance source with an operational amplifier provides a low-impedance source
and preserves common-mode rejection. Figure 2-3 shows an example of how to set up the EVM for single-supply operation with a
buffered-reference voltage connection. Depending on the application, desirable
single-supply buffer operational amplifiers include the OPA2330 and
OPA2376. The OPA2202 is a
good choice for high-voltage applications.
Install jumper shunt on positions 2 and 3 on J1
and J2
Remove resistor R5 for REFA
Remove resistor R25 for
REFB
Populate R1, R4, R6, and R7 with a 0-Ω resistor
for channel A
Populate R18, R24, R26,
and R27 with a 0-Ω resistor for channel B
Reference voltage to test point OAVinA+ (TP13)
Reference voltage to test
point OAVinB+ (TP19)
Differential input signal connect to test points
VinA– (TP14) and VinA+ (TP17) of channel A
Differential input signal
connect to test points VinB– (TP20) and VinB+ (TP22) of channel B
Observe output at test point VOA (TP15)
Observe output at test
point VOB (TP21)
Note: C15 and C22 are prepopulated with 0.1-µF
power-supply decoupling capacitors. C22 is not required to be removed for proper
single-supply operation. See the respective device data sheet for additional
power-supply decoupling information.