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Philips Semiconductors Product data
SA2411+20 dBm single chip linear amplifier for WLAN
2003 Feb 07
6
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 = Typical output power Typical small
signal Gain
Typical DC current
(no RF signal)
Typical Current
consumption
High Floating 20.0 dBm 14.5 dB 35 mA 185 mA @ 20 dBm
Low Grounded 20.0 dBm 13 dB 28 mA 185 mA @ 20 dBm
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:
P
out
+
k
V
n
detector
P
out
is output power in mWatt, V
detector
is detector voltage in Volt, k = sensitivity in mWatt/V
2
, n = quadratic factor.
The quadratic factor is 1.5. The sensitivity is then 49 mWatt/V
2
.
P
out
V
detector
(5.6 kΩ load) I
detector
(5.6 kΩ in series)
20 dBm = 100 mW 1.7 V 300 uA
19 dBm = 79 mW 1.4 V 250 uA
17 dBm = 50 mW 1.0 V 175 uA
15 dBm = 32 mW 0.7 V 125 uA
9 dBm = 8 mW 0.3 V 50 uA
The loading of the detector can be different in the application. The highest accuracy is achieved with 5.6 kΩ. 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.