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Philips Semiconductors
+20 dBm single chip linear amplifier for WLAN
8. OPERATION
The SA2411 linear amplifier is intended for operation in the 2.4 GHz band, specifically for IEEE 802.11 1 and 2 Mbits/s DSSS, and 5.5 and 11
Msymbols/s CCK standards. Throughout this document, the operating RF frequency refers to the ISM band between 2.4 and 2.5 GHz.
Amplifier Output Power
The SA2411 linear amplifier is designed to give at least 19 dBm output power for an 11 Msymbols/s CCK modulated input carrier. At 19 dBm
output power the ACPR specs are met. The fixed gain amplifier amplifies the input signal by 14.5 dB typically.
Power Mode
The biasing can be adjusted to change the gain and therefore the maximum linear output power. For high supply voltages (>3.2 V) the low-gain
mode is advised. For low supply voltages (<3.3 V) the high-gain mode is advised.
Power Mode
Pin 9 =
High
Floating
Low
Grounded
Power detector
The power detector current output is linear proportional with the RF output voltage. The RF output power is quadratic proportional to the RF
output voltage. Therefore, the detector is quadratic proportional to the output power. The following relation can be expressed:
n
P
k
V
detector
out
P
is output power in mWatt, V
out
detector
The quadratic factor is 1.5. The sensitivity is then 49 mWatt/V
P
out
20 dBm = 100 mW
19 dBm = 79 mW
17 dBm = 50 mW
15 dBm = 32 mW
9 dBm = 8 mW
The loading of the detector can be different in the application. The highest accuracy is achieved with 5.6 k . But other values can be used to
adapt to the maximum input sensitivity of other circuits. Other detector loading values result in other k-factors. The maximum detector voltage is
limited to about 2.4 V.
DC feed at input
There is a possibility to add a DC voltage at the input pins (pin 4 and pin 5) by feeding pin 2. This option should be used in case the SA2411 is
lined up with the SA2400A.
2003 Feb 07
Typical output power
Typical small
signal Gain
20.0 dBm
14.5 dB
20.0 dBm
13 dB
is detector voltage in Volt, k = sensitivity in mWatt/V
2
.
V
(5.6 k load)
detector
1.7 V
1.4 V
1.0 V
0.7 V
0.3 V
Typical DC current
(no RF signal)
35 mA
28 mA
2
, n = quadratic factor.
I
(5.6 k in series)
detector
300 uA
250 uA
175 uA
125 uA
50 uA
6
Product data
SA2411
Typical Current
consumption
185 mA @ 20 dBm
185 mA @ 20 dBm
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