Accel Instruments TS200, Руководство пользователя

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14
Amplifier CMRR Measurement
Amplifier common-mode rejection ratio or CMRR can be measure with TS200.
Figure 7 shows how to measure CMRR. CMRR measurement for amplifiers is
same as PSRR except for a few minor differences.
Source
A
B
Network
Ananyzer
TS200
Mod
Input
Output
DUT
Load
Source
A
B
Network
Ananyzer
TS200
Mod
Input
Output
DUT
Load
(a)
(b)
Figure 7. CMRR measurement setup for amplifier. (a) Calibration setup, (b)
CMRR setup.
As shown in Figure 7, the amplifier’s positive and negative inputs are
connected together and connected to the TS200’s output. Using a network
analyzer, the source is connected to the TS200 modulation input.
Set the TS200 modulation input to AC-coupled. Adjust the DC Offset knob
until the output DC voltage reaches the desired common-mode voltage (i.e. ½
VCC). Typically for CMRR measurement, the supply ripple amplitude is
200mVpp.
First the network analyzer and the TS200 need to be calibrated. Figure 7a
shows the calibration setup. The network analyzer input-A and input-B are
connected together at one point on the DUT board near the amplifier input. Set
the network analyzer to calibration mode and sweep over the frequency range
(i.e. 100Hz to 100kHz) to be measured. Save the calibration data for later use.
Refer the network analyzer manual for detailed calibration setup.
After calibration, amplifier CMRR measurement setup is shown Figure 7b. The
network analyzer input-B is moved to the amplifier output while keeping input-
A at the input. Again sweep the network analyzer over the desired frequency
range. You may refer to the network analyzer manual for details.