Current bring down when low Vramp

Hi,guys, measureing a GSM PA with low Vramp (0.5V) in burst mode, when RF source on, the current will be about 5mA less than quiescent current? But when Vramp>0.6V, the current will be reasonablly larger than quiescent current.
Why ?

This make sense, because Vramp is changing also the bias of some stages, in a dynamic mode, to be able to pass the Transient Spectrum test.