AH314
2.3-2.9 GHz WiMAX 2W Driver Amplifier
2.3 – 2.7 GHz Application Note: Changing Icq Biasing Configurations at +5V
The AH314 can be configured to operate with lower bias current by varying the bias-adjust resistors R1 & R2. R1 sets the
quiescent current in the output stage, while R2 sets the quiescent current in the input stage. The recommended circuit
configurations shown previously in this datasheet have the device operating with a 600 mA as the quiescent current (I
CQ
). This
biasing level represents a tradeoff in terms of EVM and efficiency. Lowering I
CQ
will improve upon the efficiency of the
device, but degrade the EVM performance. Raising I
CQ
will improve the EVM performance, but degrade the efficiency of the
device. Measured data shown in the plots below represents the AH314 measured and configured for 2.6 GHz applications. It is
expected that variation of the bias current for other frequency applications will produce similar performance results.
EVM vs Pout vs Icq
7
F = 2.6GHz, 802.16-2004 OFDMA, 64QAM-1/2, 1024 FFT, 20 symbols,
30 channels
6
600 mA
400 mA
500 mA
300 mA
5
EVM (%)
Table 1 : Reduced Current Operation
4
Icq
(mA)
600
500
400
300
R1
(Ω)
68
86
110
160
R2
(Ω)
150
180
300
330
V
PD,
V
bias,
V
cc
(V)
5
5
5
5
3
2
1
0
20
21
22
23
24
25
26
27
Pout (dBm)
2.3 – 2.7 GHz Application Note: Changing Icq Biasing Configurations at +3.3V
EVM vs Pout vs Icq
7
F = 2.6GHz, 802.16-2004 OFDMA, 64QAM-1/2, 1024 FFT, 20
symbols, 30 channels
6
5
Table 2 : Reduced Current Operation
Icq
R1
R2
V
PD,
V
bias,
V
cc
(mA)
(Ω)
(Ω)
(V)
3
500
3.3
3
15
400
3.3
11
24
350
3.3
17
250
43
45
3.3
EVM (%)
4
3
2
1
500 mA
350 mA
400 mA
250 mA
0
20
21
22
23
Pout (dBm)
24
25
Specifications and information are subject to change without notice.
TriQuint Semiconductor, Inc
•
Phone 1-800-WJ1-4401
•
FAX: 408-577-6621
•
e-mail: info-sales@tqs.com
•
Web site: www.TriQuint.com
Page 5 of 6 September 2008
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