8
-20 -5 0 5-15 -10 10
Pout and IP
3
(dBm), PAE (%)
POWER IN (dBm)
-10
0
10
30
20
50
40
Power
IP
3
PAE
-30 -5 0 5 10 15-15 -10 20
Pout, 3rd, 5th, 7th HARMONICS (dBm)
FREQUENCY (GHz)
-60
-50
-40
-20
-30
30
-10
0
10
20
7th
5th
3rd
Pout
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 eciency approaches 50% at
these power levels.
There are several design considerations related to reli-
ability and performance that should be taken into ac-
count when operating the amplier in saturation.
First of all, it is important that the stage preceding the
MGA-82563 not overdrive the device. Referring to the
“Absolute Maximum Ratings” table, the maximum
allowable input power is +13 dBm. This should be re-
garded as the input power level above which the device
could be permanently damaged.
Driving the amplier into saturation will also aect elec-
trical performance. Figure 17 presents the Output Pow-
er, Third Order Intercept Point (Output IP
3)
, and Power
Added Eciency (PAE) as a function of Input Power. This
data represents performance into a 50Ω 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 spe-
cic frequency and actual output power level and can be
arrived at empirically.
Increased eciency (up to 45% at full output power) is
another benet 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 fur-
ther into nonlinear operation. The 3rd, 5th, and 7th order
intermodulation products of the MGA-82563 are shown
in Figure 18 along with the fundamental response. This
data was measured in the test circuit in Figure 10.
Figure 17. Output Power, IP
3
, and Power-Added-Eciency vs. Input Power.
(V
d
= 3.0 V)
As the input power is increased beyond the linear range
of the amplier, 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
amplier less sensitive to variations in the power level
from the preceding stage. This can be a benet in sys-
tems requiring fairly constant output power levels from
the MGA-82563.
Figure 18. Intermodulation Products vs. Input Power.
(V
d
= 3.0 V)
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 al-
lows 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
at, 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. Re-
fer to the “Thermal Design Considerations” section for
more details.
