DEMO-ALM-81224 Datasheet, PDF (16/23 Pages) Broadcom Corporation. – High Linearity 1450 – 2750 MHz Variable Gain Amplifier

Application Circuit Description and Layout
Vdd1 = +5 V
Vdd2 = +5 V
C2
L1 ^{2.4 pF}
1.9 nH
~78 mA
C18
1.0 pF
RFin ^C3
7.5pF
C4
7.5pF
C1
C15 C16
0.1 PF _L2 7.5 pF 0.1 PF
5.6 nH
~270 mA
C17
2.2 PF
L3
1.0 nH
C19
0.3 pF
L4
1.9 nH
C14 _RFout
7.5 pF
C13
2.7 pF
C12 0.1 PF
C5
C7
7.5 pF 7.5 pF
C9 ^C11
7.5 pF _{7.5 pF}
0 mA 0.1 mA
0.1 mA 40 mA
Vc_att Vc1 Vc2 Vddbias = +5 V
2.4 V 4.0 V
Figure 71. Application circuit tuned for 2140 MHz operation using 0402 size external SMT components
C1
C2
L1
C3
RFIN
C17
C16
C15
L2
RFOUT
C14
876 54321
C4
C5
C6
ALM-81224
C7
C8
C9
C10
R1
1 2345678
L3 C13 L4
C11
C12
RO4350
DK 3.48
H 10 mil
W 0.57 mm
G 0.59 mm
JUNE '10
Figure 72. Demo board diagram of application circuit for 2140 MHz
Notes:
1. The VGA is capable of wideband operation from 1450-2750 MHz. Optimum linearity and Gain at different frequencies can be tuned by changing
the values of L3, L4, C13, C19 at the output match and L1, L2 at the supply lines. Table 3 below shows the optimum linearity tuning components.
2. Optimum linearity is achieved by varying Vc1 and Vc2. Typical current is as shown in the figure above.
3. If lower output power for the same linearity is desired, then the bias currents Idd1 and Idd2 can be reduced by reducing Vc1 and Vc2 respectively.
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