參數資料
型號: CX77304-15
廠商: SKYWORKS SOLUTIONS INC
元件分類: 放大器
英文描述: 2MM SOCKET STRIPS
中文描述: 824 MHz - 849 MHz RF/MICROWAVE NARROW BAND MEDIUM POWER AMPLIFIER
封裝: 9.10 X 11.60 MM, 1.50 MM HEIGHT, LEAD FREE, PLASTIC, LEADLESS, SO-16
文件頁數: 7/20頁
文件大?。?/td> 620K
代理商: CX77304-15
CX77304-15
Technical Information
PA Module for Dual-Band GSM850 PCS1900 / GPRS Applications
101749A
Skyworks Solutions, Inc.
15
September 19, 2003
Proprietary Information
Due to output impedance effects, the bias of the GaAs devices increases as the supply voltage
increases. The Voltage Clamp is designed to gradually decrease in level as the battery voltage
increases. The performance of the clamp circuit is enhanced by the band gap reference that
provides a supply-, process-, and temperature-independent reference voltage. The transfer function
relative to VBAT is shown in Figure 9. For battery voltages below 3.4 V, the base bias voltage is
limited by the common mode range of the buffer amplifier. For battery voltages above 3.4 V, the
clamp limits the base bias.
Current Buffer
The output buffer amplifier performs a vital function in the CMOS device by transferring the APC
input voltage ramp to the base of the GaAs power devices. This allows the APC input to be a high
impedance port, sinking only 10
A, typical, assuring no loading effects on the PAC circuit. The
buffers are designed to source the high GaAs base currents required, while allowing a settling time
of less than 8
s for a 1.5 V ramp.
Power Ramping Considerations for 3GPP Compliance
These are the primary variables in the power control loop that the system designer must control:
software control of the DSP / DAC
software control of the transmitter timing signals
ramp profile attributes - pedestal, number of steps, duration of steps
layout of circuit / parasitics
RC time constants within the PAC circuit design
All of these variables will directly influence the ability of a GSM transmitter power control loop to
comply with 3GPP specifications.
Figure 9. Base Bias Clamp Voltage vs. Supply Voltage
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
3.00
3.25
3.50
3.75
4.00
4.25
4.50
Vcc (Volts)
Base
Bi
as
Cl
am
p
(V
ol
ts)
clamp
101749_013b
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