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OPA333: How to understand PSRR parameters?

Part Number: OPA333
OPA333 has three PSRR parameters
1、Power supply rejection ratio : 1uV/V;
2、Long-term stability : 1uV;
3、Channel separation, DC :0.1uV/V.
My understanding

1. For example, if the input voltage is 5V, is the output ripple 5uV?
2. The long-term stable parameter means that, no matter how big the power supply ripple, can it maintain a 1uV ripple with this op amp?
3. How to understand channel separation, does the ripple rejection ratio not refer to the AC parameters?







  • There is only one PSRR spec in the OPA333 datasheet where Vos changes with the variation in the supply voltage:  ΔVos=ΔVs*PSRR so if the supply voltage changes from 5V to 2V, then Vos will typically change by: ΔVos=(5V-2V)*1uV/V=3uV.  PSRR is a measure of change in Vos with the change in the supply voltage so it has nothing to do with 5V change in the input voltage you ask above.

    The other two parameters, Long term stability and Channel separation, have nothing to do with PSRR.

    Long-term Stability simply expresses expected change in the Vos over the life of the product, which is defined as either 10 years at 25C under normal customer conditions or 300 hours at 150 deg C used to life test the part.  Note (1) basically says the Vos will typicall change by 1uV over the life of the product so if the initial Vos was, for axample, 5uV then after 10 year of constant operation at 25C Vos may become 5uV+/-1uV=4uV or 6uV.

    Channel Separation of 0.1uV/V (or -140dB) is a measure of the effect of one channel on the other. Assuming that both channels operate within the OPA333 input and output voltage linear range, this means that changing the output of one channel by 1V (or applying 1Vpp low frequency signal at the output of one channel) will result in 0.1uV change (or 0.1uVpp ripple) seen at the output of the other channel.