Pout and IP
3
(dBm), PAE (%)
Operation in Saturation for
Higher Output Power
For applications such as pre-
driver, driver, and output stages in
transmitters, the MGA-82563 can
be operated in saturation to
deliver up to 100 mW (20 dBm) of
output power. The power added
efficiency approaches 50% at
these power levels.
There are several design consider-
ations related to reliability and
performance that should be taken
into account when operating the
amplifier in saturation.
First of all, it is important that the
stage preceding the MGA-82563
not overdrive the device. Refer-
ring to the “Absolute Maximum
Ratings” table, the maximum
allowable input power is
+13 dBm. This should be regarded
as the input power level above
which the device could be perma-
nently damaged.
Driving the amplifier into satura-
tion will also affect electrical
performance. Figure 17 presents
the Output Power, Third Order
Intercept Point (Output IP
3)
, and
Power Added Efficiency (PAE) as
a function of Input Power. This
data represents performance into
a 50
Ω
load. Since the output
impedance of the device changes
when driven into saturation, it is
possible to obtain even more
output power with a “power
match.” The optimum impedance
match for maximum output power
is dependent on specific fre-
quency and actual output power
level and can be arrived at
empirically.
50
PAE
40
IP
3
30
mental response. This data was
measured in the test circuit in
Figure 10.
Pout, 3rd, 5th, 7th HARMONICS (dBm)
30
20
10
0
-10
-20
-30
-40
3rd
-50
5th
-60
-30 -15 -10 -5
7th
0
5
10
15
20
Pout
20
Power
10
0
-10
-20
-15
-10
-5
0
5
10
POWER IN (dBm)
Figure17.OutputPower,IP
3
,and
Power-Added-Efficiencyvs.Input
Power. (V
d
=3.0V)
FREQUENCY (GHz)
As the input power is increased
beyond the linear range of the
amplifier, the gain becomes more
compressed. Gain as a function of
either input or output power may
be derived from Figure 17. Gain
compression renders the amplifier
less sensitive to variations in the
power level from the preceding
stage. This can be a benefit in
systems requiring fairly constant
output power levels from the
MGA-82563.
Increased efficiency (up to 45% at
full output power) is another
benefit of saturated operation. At
high output power levels, the bias
supply current drops by about
15%. This is normal and is taken
into account for the PAE data in
Figure 17.
Like other active devices, the
intermodulation products of the
MGA-82563 increase as the device
is driven further into nonlinear
operation. The 3rd, 5th, and 7th
order intermodulation products of
the MGA-82563 are shown in
Figure 18 along with the funda-
Figure18.IntermodulationProducts
vs.InputPower.(V
d
=3.0V)
Operation at Bias Voltages
Other than 3 Volts
While the MGA-82563 is designed
primarily for use in +3 volt
applications, the internal bias
regulation circuitry allows it to be
operated with power supply
voltages from +1.5 to +4 volts.
Performance of Gain, Noise
Figure, and Output Power over a
wide range of bias voltage is
shown in Figure 19. (This data
was measured in the test circuit in
Figure 10.) As can be seen, the
gain and NF are fairly flat, but an
increase in output power is
possible by using higher voltages.
The use of +4 volts increases the
P
1dB
by over 2 dBm.
If bias voltages greater than
3 volts are used, particular
attention should be given to
thermal management. Refer to the
“Thermal Design Considerations”
section for more details.
6-215
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
