AN4016

Layout, parts list, and design considerations

Doc ID 022523 Rev 1

7/17

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Layout, parts list, and design considerations

As mentioned previously (see Figure 3), the amplifier is built with separated input-output

PCB cards:

a)

The input PCB, as shown in Figure 5, integrates the RF balun transformer, T1,

together with the RF decoupling networks.

b)

The output PCB, see Figure 7, however, relates to the design of the RF

transformer, T2, with the remaining biasing/filtering networks for the gates and

drains of STAC4932B.

An image of the assembled board is shown in Figure 1, while Table 1 gives the part list.

Figure 4, shows the final assembled board on the copper carrier and heatsink: board

robustness is an important factor in order to ensure electrical stability to manage very high

RF power.

The PCB cards are built in substrate Roger 4350B, in order to reduce dielectric losses

through the Joule effect (50 to 100 W less when compared to FR4 @ 2 kW), and in

particular to maintain thermal expansion compatibility with the copper carrier. Another

aspect of this rigid thermoset laminate allows the creation of a PCB with very good surface

finish, planarity and roughness, which are compatible with copper carrier surfaces that

support it. In fact, a carefully finished PCB surface is recommended: HAL LF with tinned

chemical deposition.

Moreover, accurate mounting procedures need to avoid bending/dirt that can compromise

the planarity of PCB cards.