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AN RFMD® APPLICATION NOTE
SZA-5044 Biasing, VPC Selection, and
Performance versus Supply Voltage
RFMD Multimarket Products Group
Overview
The SZA-5044 is a very flexible amplifier in terms of biasing. It can be run deep class AB for best efficiency and up to near class
A for the best linearity. The power on/off control voltages are accessible for each of the three stages and nominal currents are
set via externally chosen series resistors for each stage. It can support power on voltage logic (VPC) from +2.9V to +5V by simply choosing the right resistor network for the desired quiescent current and VPC power enable voltage. This application note
addresses VPC resistor selection, VPC voltage selection, associated performance tradeoffs of the various configurations over
temperature, and performance over supply voltage variation. If VCC < 3.6V is required. The STA-6033(Z) is recommended.
VPC Power Enable Bias Resistor Selection for Various VPC Voltage Levels
The schematic and table shown below describe the two recommended IQ settings of 220mA and 270mA for V+=VCC =5V. The
IQ=220mA bias has the best combination of POUT over temperature at 3% EVM (802.11a 54Mb/s). The IQ=270mA bias point
has the best IM3 performance as compared to IQ=220mA. Table 1 shows resistor values for VCC =5V and VPC range of 2.9V–
5V. Table 2 shows resistor values for other combinations of VCC and VPC levels.
Figure 1. Application Schematic
RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks and registered trademarks are the property of their respective owners. ©2006, RF Micro Devices, Inc.
AN062 090416
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or [email protected]
1 of 5
SZA-5044 Biasing, VPC Selection, and Performance versus Supply Voltage
Table 1
VPC =2.9V to 5.0V
ICQ =220mA
VCC =5V
Stage 1
(41mA)
Stage 2
(94mA)
VPC
R1 (Ω)
R2 (Ω)
R3
ICQ =270mA
Stage 3
(85mA)
R4 (Ω)
R5
Stage 1
(41mA)
Stage 2
(94mA)
R1 (Ω)
R2 (Ω)
Stage 3 (135mA)
R3
R4 (Ω)
R5
2.9
0
698
OUT
221
OUT
0
698
OUT
10
OUT
3
174
1.10K
OUT
604
OUT
174
1.10K
OUT
261
OUT
3.1
348
1.37K
OUT
909
OUT
348
1.37K
OUT
499
OUT
3.2
511
1.78K
OUT
1.24K
OUT
511
1.78K
OUT
750
OUT
3.3
698
2.15K
OUT
1.50K
OUT
698
2.15K
OUT
1.00K
OUT
5
3.74K
2.49K
7.5K
7.15K
OUT
3.74K
2.49K
7.5K
2.6K
7.5K
Table 2
VCC =4.9V to 5.5V and VPC =2.9V to 5.0V
ICQ =220mA
Stage 1
(41mA)
Stage 2
(94mA)
R1 (Ω)
R2 (Ω)
ICQ =270mA
Stage 3
(85mA)
Stage 1
(41mA)
Stage 2
(94mA)
R1 (Ω)
R2 (Ω)
Stage 3 (135mA)
VCC (V)
VPC (V)
4.9
2.9
0
200
OUT
249
OUT
0
200
OUT
0
OUT
4.9
3
182
412
OUT
562
OUT
182
412
OUT
237
OUT
R3
R4 (Ω)
R5
R3
R4 (Ω)
R5
4.9
3.1
365
604
OUT
909
OUT
365
604
OUT
475
OUT
4.9
3.2
562
825
OUT
1.21K
OUT
562
825
OUT
698
OUT
4.9
3.3
698
1.02K
OUT
1.50K
OUT
698
1.02K
OUT
1.00K
OUT
5.1
2.9
0
243
OUT
301
OUT
0
243
OUT
20
OUT
5.1
3
182
442
OUT
619
OUT
182
442
OUT
274
OUT
5.1
3.1
340
665
OUT
1.00K
OUT
340
665
OUT
511
OUT
5.1
3.2
511
825
OUT
1.24K
OUT
511
825
OUT
750
OUT
5.1
3.3
698
1.10K
OUT
1.62K
OUT
698
1.10K
OUT
1.02K
OUT
5.1
5
3.74K
2.61K
7.5K
7.32K
OUT
3.74K
2.61K
7.5K
2.8K
7.5K
5.2
2.9
10
249
OUT
332
OUT
10
249
OUT
49.9
OUT
5.2
3
174
475
OUT
665
OUT
174
475
OUT
301
OUT
5.2
3.1
348
681
OUT
1.02K
OUT
348
681
OUT
562
OUT
5.2
3.2
562
887
OUT
1.37K
OUT
562
887
OUT
825
OUT
5.2
3.3
698
1.10K
OUT
1.69K
OUT
698
1.10K
OUT
1.10K
OUT
5.2
5
3.74K
2.61K
7.5K
7.50K
OUT
3.74K
2.61K
7.5K
2.87K
7.5K
5.3
2.9
10
274
OUT
348
OUT
10
274
OUT
82.5
OUT
5.3
3
196
499
OUT
698
OUT
196
499
OUT
340
OUT
5.3
3.1
357
750
OUT
1.02K
OUT
357
750
OUT
604
OUT
5.3
3.2
511
909
OUT
1.37K
OUT
511
909
OUT
825
OUT
5.3
3.3
698
1.15K
OUT
1.74K
OUT
698
1.15K
OUT
1.10K
OUT
5.3
5
3.74K
2.67K
7.5K
7.68K
OUT
3.74K
2.67K
7.5K
3.0K
7.5K
5.4
2.9
0
287
OUT
374
OUT
0
287
OUT
100
OUT
5.4
3
182
511
OUT
750
OUT
182
511
OUT
348
OUT
5.4
3.1
357
750
OUT
1.10K
OUT
357
750
OUT
604
OUT
AN062 090416
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or [email protected]
2 of 5
SZA-5044 Biasing, VPC Selection, and Performance versus Supply Voltage
Table 2
5.4
3.2
562
1.00K
OUT
1.37K
OUT
562
1.00K
OUT
887
OUT
5.4
3.3
698
1.18K
OUT
1.78K
OUT
698
1.18K
OUT
1.13K
OUT
5.4
5
3.74K
2.67K
7.5K
7.68K
OUT
3.74K
2.67K
7.5K
3.16K
7.5K
5.5
2.9
0
301
OUT
383
OUT
0
301
OUT
100
OUT
5.5
3
174
511
OUT
750
OUT
174
511
OUT
357
OUT
5.5
3.1
340
750
OUT
1.10K
OUT
340
750
OUT
619
OUT
5.5
3.2
511
1.00K
OUT
1.47K
OUT
511
1.00K
OUT
909
OUT
5.5
3.3
698
1.21K
OUT
1.78K
OUT
698
1.21K
OUT
1.18K
OUT
5.5
5
3.74K
2.67K
7.5K
8.06K
OUT
3.74K
2.67K
7.5K
3.32K
7.5K
The temperature range and required performance of the application should be considered when choosing a VPC power enable
voltage. The higher VPC values have better performance over temperature because IQ varies less with temperature. Below is
Figure 2 that shows IQ variation over temperature for VPC enable set voltages ranging from 2.9V to 5V.
.
Figure 2. SZA-5044 ICQ versus VPC versus Temperature
AN062 090416
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or [email protected]
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SZA-5044 Biasing, VPC Selection, and Performance versus Supply Voltage
Another consideration is the variation in VPC enable voltage and the impact on performance. Performance is optimized when
the VPC power enable is regulated and controlled. This is the case for the Atheros chip set where a regulated VPC enable=2.9V
is available. Figure 3 shows IQ versus swept VPC for the nominal cases of VPC enable=2.9V to 5V at 25°C.
.
Figure 3. SZA-5044 ICQ versus Swept VPC, Constant VCC =5V, T=25°C
The variation in current over temperature has impact on EVM over temperature. Figure 4 shows the EVM at POUT =21.5dBm
versus temperature and VPC enable set voltage.
.
Figure 4. EVM (%) at POUT =21.5dBm versus VPC versus Temp
AN062 090416
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or [email protected]
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SZA-5044 Biasing, VPC Selection, and Performance versus Supply Voltage
The variation in VCC also has an impact on EVM. Figure 5 shows the POUT at 3% EVM versus temperature and fixed VPC
voltage=5.0V.
.
Figure 5. POUT at 3% EVM versus VCC, F=2.4GHz, Constant VPC =5V, ICQ=302mA
AN062 090416
7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical
support, contact RFMD at (+1) 336-678-5570 or [email protected]
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