We need to provide a stable bias-t condition for our device in any amplifier application. Bipolar transistors: Must force the DC (average) value of VCE and IC to desired values and keep them constant using feedback techniques.

Never fix VBE: IC = ISE e VBE/VT . IC varies exponentially with temperature. Never fix IB: IC =
IB
varies tremendously from device to device and increases with temperature as well (0.7%/degree C).

Referring again to Fig. 1, the BJT circuit uses the conventional 4 resistor bias approach where the emitter resistor provides negative feedback stabilization against drift of the bias tee point with temperature or device parameter variation from batch to batch of devices. But, these circuits are not often used for RF applications because the biasing resistances also load the circuit and reduce the gain. 

Therefore, bias tees circuit techniques that permit use of a directly grounded source or emitter connection are preferred for high frequency amplifiers when implemented using discrete components on PC boards. In RFIC implementations, more flexibility is possible. One can use CC, CB, CG, CD connections as well as choosing device areas to optimize circuit performance.