AD8314

Rev. B | Page 17 of 20

VSET (V)

Figure 40 shows the relationship between the setpoint voltage,

function is linear in dB for a dynamic range of over 40 dB.

Figure 41 shows a similar circuit for a single band handset

power amplifier. The BGY241 (Phillips) is driven by a nominal

power level of 0 dBm. A 20 dB directional coupler, DC09-73

(Alpha), is used to couple the signal in this case. Figure 42

shows the relationship between the control voltage and the

output power at 0.9 GHz.

In both of these examples, noise on the V_DN pin can be reduced

control pin of the power amplifier. However, the value of the

resistor should be kept low to minimize the voltage drop across

it due to the dc current flowing into the gain control input.

40

–30

01.2

30

20

10

0

–10

–20

0.2

0.4

0.6

0.8

1.0

Figure 40. POUT vs. VSET at 0.9 GHz for Dual Mode Handset Power Amplifier

Application

2.7V

VSET

0V TO 1.1V

0dBm

MAX

ATTN

15dB

220pF

TO

ANTENNA

52.3Ω

1

2

3

4

ENBL

RFIN

AD8314

8

7

6

5

VSET

FLTR

V_DN

VPOS

COMM

V_UP

0.1µF

RF INPUT

35dBm

MAX

47µF

BGY241

15dBm

2.2µF

680pF

0dBm

DC09-73

6

3

4

5

12

3.5V

Figure 41. A Single Mode Power Amplifier Control Circuit

40

–50

0

VSET (V)

30

20

10

0

–10

–20

–30

–40

0.2

0.4

0.6

0.8

1.0

Figure 42. POUT vs. VSET at 0.9 GHz for Single Mode Handset