low voltage radio frequency amplifier
A common emitter amplifier made using a Bipolar Transistor (BJT) only needs 0.6V~0.7V to function, but with only a 0.9V supply you won't get much voltage swing on the output.
Also with only 1mA available the output impedance of the amplifier would need to be several hundred ohms minimum, so you are not going to get much power out of it.  You don't have enough voltage to make a class AB amplifier output stage (you would need something greater than 1.4V)
There are some very low voltage MOSFETS such as the BSH105 (0.45V threshold).
https://assets.nexperia.com/documents/data-sheet/BSH105.pdf
Texas Instruments makes an OP-AMP LMV951 that can operate on as little as 0.9V.
https://www.ti.com/lit/ds/symlink/lmv951.pdf?HQS=TI-null-null-digikeymode-df-pf-null-wwe&amp;ts=1607313906248
The gain bandwidth product is only 2.7MHz so its really only suitable for use up to 100s of kHz.