ESR of bypass & decoupling capacitor

they don't bypass!

What's the adequate range of ESR with Tantalum cap ?
Thanks.

A typical 10uF Tantalum capacitor ESR measures from 1.2 to 0.8 Ohms ..
The ultra-low ESR series will have the ESR below 100mΩ (0.1Ω) with typical values below 35mΩ ..

Regards,
IanP

What's the recommended range of Tan. Cap ESR value for decoupling use of PA ?
Theoretically, low ESR is better but what's the adequate ESR value for PA use ?
Thanks a lot.

There is no recommendation as such ..
I would say - the lower ESR the better ..

Regards,
IanP

The question did not specify frequency range of interest.
Tantalum 10uF maybe good in audio range.
If we are interested in GHZ, as the FORUM index suggests, Tantalum
is not a good choice.