RF5152_11 Datasheet, PDF (5/10 Pages) RF Micro Devices – LINEAR POWER AMPLIFIER

RF5152
Theory of Operation and Application Information
The RF5152 is a three-stage power amplifier (PA) with a minimum gain of 32dB (34dB typical) in the 2.4GHz to 2.5GHz Indus-
trial, Scientific, and Medical (ISM) band. The RF5152 has a 50 internal input and interstage match. Only the RF5152 output
stage requires matching. The RF5152 is designed primarily for IEEE802.11g/n wireless local area network (WiFi) applications
where the available supply voltage and current are limited. This amplifier will operate to and below the lowest expected voltage
made available by a typical PC Card (PCMCIA or CardBus) slot in a laptop personal computer (PC). The RF5152 maintains
required linearity at decreased supply voltages.
The RF5152 operates from a single supply voltage of 3.0V_DC to 3.6V_DC to deliver specified performance. Power control is pro-
vided through two (2) bias control input pins (VB1/VB2 and VB3). In most applications these two (2) bias control input pins are
connected together and employed as a single control input. The RF5152 has been primarily characterized with a VB voltage of
2.8V_DC. However, the RF5152 will operate from a wide range of bias control voltages and within a wide range of frequencies
(typically 1800MHz to 2800MHz). If a bias control voltage other than 2.8V_DC is preferred or if a different frequency range
(other than 2.4GHz to 2.5GHz) is desired, please contact RFMD Sales or Applications Engineering for assistance.
Though not difficult to implement to achieve state-of the-art performance, the RF5152 is employed at frequencies greater than
2GHz, where care in circuit layout and component selection is advisable. Of primary concern with RF5152 PCB layout is the
selection and placement of output matching components (RF5152PCBA bill of materials (BOM) is available upon request).
High-Q (quality factor) capacitors and inductors are not required in every RF5152 based design; however, it is highly recom-
mended that the RF5152PCBA evaluation board BOM be followed exactly for all initial end product designs. Upon initial base-
line of RF5152 based PCB performance, less costly (Lower-Q) output matching circuit components may be substituted and
evaluated against the initial design performance. RFMD experience indicates that end product FTY improvements more than
offset the cost difference between “High-Q” and “Low-Q” components.
There is no required matching on the RF5152 input or interstage circuits. Only the RF5152 output stage requires matching
allowing the RF5152 to be implemented in applications requiring the fewest end product bill of materials (BOM) parts count
and lowest BOM cost. The input stage requires a DC-blocking capacitor. In most cases the capacitor used as part of the
RF5152 output matching circuit is also employed to accomplish DC-blocking. The RF5152PCBA evaluation board (available
from RF Micro Devices, Inc. (RFMD)) is optimized for 3.3V_DC supply input. The output matching capacitor is C10 which is
located approximately 120mils from the IC (as shown on the RF5152PCBA Evaluation Board Schematic). The capacitor C10 is
selected in value and positioned with reference to 50 transmission line segment TL1. Transmission line segment TL1 should
be duplicated as closely as possible in specified length and thickness in any customer PCB layout. Due to PCB material varia-
tion (e.g., FR4) and PCB manufacturer variations, the customer may benefit from small adjustments made to the length of TL1
when the RF5152PCBA evaluation board is duplicated to produce an end product PCB design. The initial PCB layout should
include exposed ground area near C10 to allow ease of RF5152 output circuit optimization. Smith Chart-based design tools
may be used to assist in determining the desired capacitor value and transmission line physical characteristics. Note that the
use of a single capacitor output circuit match will result in a more sensitive match and slightly reduced RF5152 bandwidth. In
this configuration the RF5152 will exhibit sufficient output spectrum bandwidth to meet IEEE802.11b/g requirements when
matched properly.
For best results, the RF5152PCBA evaluation board circuit layout should be copied as closely as possible. In particular, the
RF5152PCBA evaluation board ground layout, ground vias, and output matching components and location should be copied
without deviation. Other PCB layout configurations may provide acceptable RF5152 performance; however, the end product
design process will be faster and manufacturing first time yield (FTY) better if the RF5152PCBA evaluation board design is fol-
lowed. RFMD provides RF5152PCBA design and Gerber files upon request.
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