12
LDO
TS200
Mod
Input
Output
DUT
Load
Function
Generator
Or AWG
Oscilloscope
CH1
CH2
Figure 5. PSRR measurement using an oscilloscope.
Using the oscilloscope, one can measure the amplitude voltage at CH1 and CH2.
Divide CH2 by CH1 is the PSRR. One can use the below equation for PSRR
calculation in dB.
PSRR = 20log(CH2/CH1)
If PSRR is better than 40dB, it is recommended to increase the TS200 output
ripple voltage to 500mVpp due to oscilloscope has lower sensitivity than
network analyzer.
Amplifier PSRR Measurement
The TS200 is also ideal for amplifier power supply rejection ratio
measurements, especially power amps operating at maximum load conditions.
Such amplifiers as audio amplifiers (class-A, B, AB, D and G) with heavy
loading are ideal for TS200. The TS200 can also measure PSRR for op-amps,
differential amplifiers, unity gain buffers, digital-to-analog converters, and
analog-to-digital converters, etc.
Op amp PSRR measurement is same as LDO except for a few minor
differences. Please see Figure 6 and refer to the previous section, “
LDO PSRR
Measurement
”, for amplifier PSRR measurement.
