18.0-21.0/36.0-42.0 GHz GaAs MMIC
Doubler and Power Amplifier
September 2005 - Rev 01-Sep-05
20DBL0629
App Note [1] Biasing
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It is recommended to separately bias each amplifier stage Vd1 through Vd6 at Vd1=2.5V, Vd2=3.0V, Vd(3,4,5,6)=4.5V with
For Parallel Stage Bias (Recommended for general applications) -- The same as Individual Stage Bias but all the drain pad DC bypass capacitors
(~100-200 pF) can be combined. Additional DC bypass capacitance (~0.01 uF) is also recommended to all DC or combination (if gate or drains are
tied together) of DC bias pads. Vd(3,4,5,6) or Vg(3,4,5,6) have been tied together but can be left open.
For Individual Stage Bias (Recommended for saturated applications) -- Each DC pad (Vd1,2,3,4,5,6 and Vg1,2,3,4,5,6) needs to have DC bypass
capacitance (~100-200 pF) as close to the device as possible. Additional DC bypass capacitance (~0.01 uF) is also recommended.
MTTF Tables
These numbers were calculated based on accelerated life test information and thermal model analysis received from the fabricating foundry.
od
Rth
TBD
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Backplate
Temperature
55 deg Celsius
75 deg Celsius
95 deg Celsius
Channel
Temperature
TBD
TBD
MTTF Hours
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FITs
TBD
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Mimix Broadband, Inc., 10795 Rockley Rd., Houston, Texas 77099
Tel: 281.988.4600 Fax: 281.988.4615 mimixbroadband.com
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App Note [2] Bias Arrangement
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Page 4 of 6
Characteristic Data and Specifications are subject to change without notice.
©2005
Mimix Broadband, Inc.
Export of this item may require appropriate export licensing from the U.S. Government. In purchasing these parts, U.S. Domestic customers accept
their obligation to be compliant with U.S. Export Laws.
n
Id1<1mA, Id2=20mA, Id3=40mA, Id4=70mA, Id5=150mA, Id6=270mA. Separate biasing is recommended if the amplifier is to be used at high levels
of saturation, where gate rectification will alter the effective gate control voltage. As shown in the bonding diagram, it is possible to parallel stages
Vd(3,4,5) with Id(3,4,5)=260mA while maintaining satisfactory performance. For non-critical applications it is possible to parallel stages Vd(3,4,5,6)
together and adjust the common gate voltage Vg(3,4,5,6) for total drain current Id(total)=530mA. It is also recommended to use active biasing to
keep the currents constant as the RF power and temperature vary; this gives the 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 of the pHEMT is controlled to maintain correct drain current and thus
drain voltage. The typical gate voltage needed to do this is -0.7V. Typically the gate is protected with Silicon diodes to limit the applied voltage. Also,
make sure to sequence the applied voltage to ensure negative gate bias is available before applying the positive drain supply.
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