Hello Guys,
                       I am working on OTA design and wants to measure the power supply sensitivity which is  basically gain from power supply to output. I am using just single supply of 5 volts.

                         The way I am measuring this is I am connecting small ac supply to power supply terminal VDD and measuring the output voltage. The ratio is the required sensitivity. But I am not sure about this.

If any one help me with this that would be grateful. 8-)

As with everything there is alternative approach.

You can use XF analysis, then you won't have to play around with AC sources at supply.

I've learned this method from nice presentation by Jonathan David from Cadence titled    Characterizing Differential Amplifiers for Communications Circuits - Measuring Performance with Simulation for First Pass Success. You can find pdf by googling the title.