SZA-2044 Biasing, V PC Selection, and Performance versus Supply Voltage

Transcription

1 AN RFMD APPLICATION NOTE SZA-2044 Biasing, V PC Selection, and Performance versus Supply Voltage RFMD Multimarket Products Group Overview The SZA-2044 is a very flexible amplifier in terms of biasing It can run deep class AB for best efficiency and up to near class A for 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 (V PC ) from +29V to +5V by simply choosing the right resistor network for the desired quiescent current and V PC power enable voltage This application note addresses V PC resistor selection, V PC voltage selection, associated performance tradeoffs of the various configurations over temperature, and performance over supply voltage variation V PC Power Enable Bias Resistor Selection for Various V PC Voltage Levels Information is shown below for the recommended I Q setting of 302mA for V+=V CC =5V Table 1 shows resistor values for V CC =5V and V PC range of 29V 5V Table 2 shows resistor values for other V CC and V PC level combinations 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, USA 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 1 of 5

2 Table 1 V PC =29V to 50V ICQ=302mA V CC =50V Stage 1 (75mA) Stage 2 (227mA) V PC R1 (Ω) R2 (Ω) R5 (Ω) Table OUT OUT OUT OUT OUT 5 182K 110K 475K ICQ=302mA Stage 1 (75mA) Stage 2 (227mA) V CC =49V to 55V V PC =29V to 5V R1 (Ω) R2 (Ω) R5 (Ω) OUT OUT OUT OUT OUT K 110K 475K OUT OUT OUT OUT OUT K 110K 475K OUT OUT OUT OUT OUT K 110K 475K OUT OUT OUT OUT OUT K 113K 475K OUT OUT OUT OUT OUT 2 of 5

3 Table K 115K 475K OUT OUT OUT OUT OUT K 115K 475K OUT OUT OUT OUT OUT K 115K 475K OUT OUT OUT OUT OUT K 118K 475K The temperature range and required performance of the application should be considered when choosing a V PC power enable voltage The higher V PC values have better performance over temperature because Iq varies less with temperature Figure 2 shows Iq variation over temperature for V PC enable set voltages ranging from 29V to 5V 450 SZA-2044 Icq vs Vpc vs Temp Icq(mA) Temp(C) Vpc(V) 2 9v 3 0v 3 1v 3 2v 3 3v 5v Figure 2 SZA-2044 I CQ versus V PC versus Temperature 3 of 5

4 Another consideration is the variation in V PC enable voltage and the impact on performance Performance is optimized when the V PC power enable is regulated and controlled Figure 3 shows I Q versus swept V PC for the nominal cases of V PC enable=29v to 5V at 25 C 05 SZA-2044 Icq vs swept Vpc, Constant Vcc=5V, T=25C (Icq=302mA) 04 Icq(A) Vpc Config VPC(V) 29v 30v 31v 32v 33v 5v Figure 3 SZA-2044 I CQ versus Swept V PC, Constant V CC =5V, T=25 C The variation in current over temperature has impact on EVM over temperature Figure 4 shows the EVM at P OUT =225dBm versus temperature and V PC enable set voltage Pout=225dBm vs Vpc vs Temp, F=24GHz EVM(%) Temp(C) Vpc Config 29v 3v 33v 5v Figure 4 EVM (%) at P OUT =225dBm versus V PC versus Temp, F=24GHz 4 of 5

5 The variation in V CC also has an impact on EVM Figure 5 shows the P OUT at 3% EVM versus temperature and fixed V PC voltage=50v % EVM vs Vcc, F=24GHz, Constant Vpc=5V, Icq=302mA Pout(dBm) Vcc(V) -40c -20c 0c +25c +70c +85c Figure 5 P OUT at 3% EVM versus V CC, F=24GHz, Constant V PC =5V, ICQ=302mA 5 of 5