THS4521 Datasheet, PDF (27/65 Pages) Texas Instruments – VERY LOW POWER, NEGATIVE RAIL INPUT, RAIL-TO-RAIL OUTPUT, FULLY DIFFERENTIAL AMPLIFIER

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THS4521, THS4522, THS4524
SBOS458H – DECEMBER 2008 – REVISED JUNE 2015
Feature Description (continued)
8.3.4 Common-Mode and Power-Supply Rejection
The circuit shown in Figure 57 is used to measure the CMRR. The signal from the network analyzer is applied
common-mode to the input. Figure 58 is used to measure the PSRR of V_S+ and V_S–. The power supply under
test is applied to the network analyzer dc offset input. For both CMRR and PSRR, the output is probed using a
Tektronix high-impedance differential probe across the 953-Ω resistor and referred to the amplifier output by
adding back the 0.42-dB as a result of the voltage divider on the output. For these tests, the resistors are
matched for best results.
V_IN+
From
Network
Analyzer
1 kW
1 kW
V_S+
Calibrated
Differential 52.3 W
Probe
Open
PD
0.22 mF
THS452x
V_OCM
V_S-
24.9 W
24.9 W
Measure with
953 W Differential
Probe
Open
0.22 mF
1 kW
1 kW
Figure 57. CMRR Test Circuit
Open
Open
Open
Power
Supply
Network
Analyzer
1 kW
52.3 W
PD
0.22 mF
1 kW
52.3 W
1 kW
V_S+
Calibrated Differential
Probe
Across
V_S+ and GND
THS452x
V_OCM
V_S-
1 kW
24.9 W
24.9 W
Measure with
Differential
953 W
Probe
Across R_OT
Open
0.22 mF
Figure 58. PSRR Test Circuit
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