device intrinsic capacitance

[pragash]

In the PCB design world, we have to select an RF device/transistor and design the circuit arround it in order to design an RF Power Amplifier (PA). Is the transistor's intrinsic capacitance (Cgs, Cds, Cgd) are an important consideration for PCB design? we usually will only look at output power, efficiency to select transistor, and not intrinsic capacitance. How significant is device intrinsic capacitance in selecting a device/transistor?

 

[dick_freebird]

Intrinsic capacitances may be "rolled up" into datasheet params like fT/Fmax, or the S-params / SPICE models you'd use for refining the design - in PCB world you change the P/N, in IC design you change the master and its available parameters.

I don't start with capacitances, but I will look at them if something isn't going right. Since in IC design the capacitance depends from the geometry params and the device master, they're a "result" more than an "input".