AN4016

Design choices

Doc ID 022523 Rev 1

3/17

1

Design choices

The main objectives of the 2 kW power amplifier design are board compactness (100 x 150

mm), full SMT technology, and to avoid the use of ferromagnetic components and coaxial

transmission line transformers.

In summary, see circuit diagram in Figure 3, the power amplifier uses double push-pull bolt-

down devices, 2 x STAC4932B (see Figure 2) operate in Class AB. The two STACs are

driven in push-pull through the transformer T1 together with two in-phase power splitters:

this choice seems to be the best topology layout in terms of circuit size and mechanical

compactness. Moreover, as the temperature coefficient of MOSFET channel resistance is

positive, this makes a short-circuit possible in each pair of STAC4932B drains.

Figure 2.

STAC244B bolt-down package

Figure 3.

STEVAL-IMR002V1 circuit diagram

P1_RF INPUT

SMA_Female

P2_RF OUTPUT

N_Female

GND

GND

Q3

Q4

Q2

Q1

GND

GND

C31

C32

GND

R13

C9

C14

GND

GND

+

C6

GND

C21

C40

R4

C18

R6

R8

R10

R12

R14

R15

C41

GND

R19

R20

R21

R25

R26

R27

GND

VCC

+

C13

+

C12

GND

GND

C23

C28

C30

GND

R17

R22

R3

Vg1

C34

C16

GND

+

C3

GND

GND

L2

C7

C10

GND

GND

+

C15

GND

R7

C8

C11

GND

GND

C17

T1

T2

L14

L3

R30

R1

C57

GND

GND

C58

L5

R24

Vg2

C48

+

C47

GND

GND

L13

C49

C52

GND

GND

+

C51

GND

R29

C50

C53

GND

GND

L15

GND

L10

L8

L16

L12

L4

GND

C2

GND

R11

R16

C24

GND

C20

C36

C45

R31

C55

GND

GND

GND

GND

GND

R28

R5

R9

GND

GND

C33

C37

C26

C25

Rm

(~5 V typ)

(~5 V typ.)

(+100 V)

D1

LED

R32

GND

R33

GND

R34

R35

GND

C60

C59

C61

C63

C62

C64

VBIAS_1

VBIAS_1

VBIAS_1

VBIAS_2

VBIAS_2

VBIAS_2

GND

GND

Rm

GND

GND

C29

GND

GND

C42

J1

J2

J3

GND

Line_Bridge

GND

GND

1

2

3

CON3

1

2

3

CON3

Vg1

GND

GND

Vg2

CON1

CON1

GND

Input Board 3 layer

Output Board 2 layer

C4

AM10220V1