CIRCUIT CONSIDERATIONS

At high power levels (500 W and up), the circuit layout be-

comes critical due to the low impedance levels and high RF

currents associated with the output matching. Some of the

components, such as capacitors and inductors must also

withstand these currents. The component losses are directly

proportional to the operating frequency. The manufacturers

specifications on capacitor ratings should be consulted on

these aspects prior to design.

Push–pull circuits are less critical in general, since the

ground referenced RF loops are practically eliminated, and

the impedance levels are higher for a given power output.

High power broadband transformers are also easier to de-

sign than comparable LC matching networks.

EQUIVALENT TRANSISTOR PARAMETER TERMINOLOGY

Collector

Drain

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Emitter

Source

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Base

Gate

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

V(BR)CES

V(BR)DSS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

VCBO

VDGO

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

IC

ID

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ICES

IDSS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

IEBO

IGSS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

VBE(on)

VGS(th)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

VCE(sat)

VDS(on)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cib

Ciss

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cob

Coss

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

hfe

gfs

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

RCE(sat) =

VCE(sat)

IC

rDS(on) =

VDS(on)

ID

6

REV 2