generating a rippled VDD

[quintessential]

i'm trying to do some power supply ripple rejection tests, this requires my DC input to my circuit to have a ripple on it so i can study the ripple at the output, my question is how does one juxtapose AC and DC.There are other concerns but for now i just want to get the ball rolling, lets pretend i have every circuit design tool and part available,any ideas?

 

[TrevorP]

Bias an AC current?

 

[Styx]

series an AC source

 

[RadioRon]

Put a power transformer secondary in series with your DC and drive its primary with whatever AC you like.

 

[quintessential]

ok, sounds good...forsee any bandwidth limitations? i'm thinking of testing up to 20Mhz

 

[Sceadwian]

A power transformer isn't going to work at 20mhz. How about using a power BJT or FET between the load and the ground? Bias the transistor as close to saturation as you can and you can drive the base for your AC ripple at whatever frequency the transistor will allow.

 

[quintessential]

hmm i'm still researching it but Scadwian driving the base of a power FET in the triode region will create a rippled VDD at the drain??