PSRR Test Fixture - Questions

i have to design a test fixture for measuring PSRR - power supply rejection ratio - for a sample-and-hold (track and hold) amplifier.

The test procedure says to add a 2.4 KHz sine wave to the Vcc which is 15 volts in this case and measure the signal on the output. The expected PSRR is -30 dB min. I thought of using a transformer to couple the ac onto the positive power supply and adjust the positive voltage to get +15 V, 55 mA at the VCC input of the IC. But I am confounded by the specifications of audio transformers to accomplish this. I know I want a 1:1 but not 600 ohm impedance. I understand I should not put decoupling capacitors on the power supply inputs of the device and that I probably want a "swamping capacitor" on the voltage terminals. But what I don't know is what type of transformer and what parameters I should be looking for.
Note: I don't want to wind my own transformer - there are plenty on the market.

Any suggestions welcomed. I can't measure the IC yet as it hasn't been produced yet. It is an old design of an obsolete part and the design engineers are long gone.

Thanks

You can try something like the circuit below. Make R1 adjustable to set the average output voltage. You should then have a DC source with ripple. The 2.4 kHz injection level can be changed to suit your requirements. The resistor R2 on the output just represents the load that your test circuit will have.

Alternatively, you can use a 12 V regulator and control the output voltage by the DC-offset of a suitable function generator connected as shown.

Injecting signal by a transformer is a way to go.
You need to be measuring supply rail AC magnitude
and output AC magnitude at once. Then impedance
of the xfmr is a "don't-care" because you know the
two quantities for the calculation.

Now, at some point you will leave small signal domain
where PSRR is the classical linear (log) expression and
get into large signal phenomena. You might want to
start from a known "small" signal point and run up the
amplitude to whatever the dictated stimulus amplitude
may be, looking for inflection points.

Dick_freebird
Do I pick an audio transformer that can handle 55 mA in t he primary and has 1:1 turns ratio. Also works in the 2.4kHz frequency range?
E-Design
The regulator circuit looks rather straight forward except for output capacitors for stability. Or do I neglect to put them in and let the circuit oscillate to the 2.4KHz signal?
Piper

The idea I proposed came from an application in an old National 1980 data book. I have not seen it in more modern data sheet application notes. You can use the input capacitance shown for required stability.

The posted diagram shows an example where VG1 is represented by this power AM Modulator.

Some oscilloscopes can be used to perform this math function to calculate 20log(Vin/Vout) for you with using AC coupled inputs. Ideally, a FRA should be used.
https://www.youtube.com/watch?v=TBpOOVmnJos