XP1027-BD_15 Datasheet, PDF (9/10 Pages) M/A-COM Technology Solutions, Inc. – Power Amplifier

XP1027-BD
Power Amplifier
27 - 31 GHz
App Note [1] Biasing -
It is recommended to separately bias each
amplifier stage V_D1 through V_D3 at V_D (1,2,3) = 5 V
with I_D1 = 240 mA, I_D2 = 630 mA and I_D3 = 1240
mA. Separate biasing is recommended if the
amplifier is to be used in a linear application or at
high levels of saturation, where gate rectification
will alter the effective gate control voltage. For
non-critical applications it is possible to parallel all
stages and adjust the common gate voltage for a
total drain current I_D (total) = 2110 mA.
Linear Applications -
For applications where the amplifier is being used
in linear operation, where best IM3 (Third-Order
Intermod) performance is required at more than
5 dB below P1dB, it is recommended to use active
gate biasing to keep the drain currents constant as
the RF power and temperature vary; this gives the
best performance and most reproducible results.
Depending on the supply voltage available and the
power dissipation constraints, the bias circuit may
be a single transistor or a low power operational
amplifier, with a low value resistor in series with the
drain supply used to sense the current. The gate
voltage of the pHEMT is controlled to maintain
correct drain current compensating for changes
over temperature.
Rev. V2
Saturated Applications -
For applications where the amplifier RF output
power is saturated, the optimum drain current will
vary with RF drive and each amplifier stage is best
operated at a constant gate voltage. Significant
gate currents will flow at saturation and bias
circuitry must allow for drain current growth under
this condition to achieve best RF output power and
power added efficiency. If the input RF power level
will vary significantly, a more negative gate voltage
will result in less die heating at lower RF input drive
levels where the absence of RF cooling becomes
significant. Under this bias condition, gain will then
vary with RF drive
NOTE -
For any application it is highly recommended to
bias the output amplifier stage from both sides for
best RF and thermal performance.
CAUTION -
Make sure to properly sequence the applied
voltages to ensure negative gate bias (V_G1,2,3) is
available before applying the positive drain supply
(V_D1,2,3). It is recommended that the device gates
are protected with silicon diodes to limit the applied
voltage.
Bias Arrangement
2
3
4
5
6
7
1 RF_IN
RFOUT 8
14
13
12
11
10
9
Layout for reference only – It is recommended to bias output
stage from both sides.
9
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