26TX0555 Datasheet, PDF (6/9 Pages) Mimix Broadband – 18.0-36.0 GHz GaAs MMIC Transmitter

18.0-36.0 GHz GaAs MMIC
Transmitter
August 2005 - Rev 04-Aug-05
26TX0555
App Note [1] Biasing - As shown in the bonding diagram, this device is operated by separately biasing Vd(1,2,3)=5.0V,
Vss=-5.0V, Id1=230mA, Id2=140mA, Id3=75mA and Iss=50mA. Additionally, a mixer and doubler bias are also required
with Vg3=Vg4=-0.5V. Adjusting Vg3 and Vg4 above or below this value can adversely affect conversion gain, LO/RF
isolation and intercept point performance. Gain control can be adjusted by varying Vg1 from 0.0 to -1.2 V with 0.0 V
providing minimum attenuation and -1.2 V providing maximum attenuation. 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
n ^{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 -0.2V. 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.
o _{App Note [2] Bias Arrangement -}
i _{For Parallel Stage Bias (Recommended for general applications) -- The same as Individual Stage Bias but all the drain or}
t _{gate pad DC bypass capacitors (~100-200 pF) can be combined. Additional DC bypass capacitance (~0.01 uF) is also}
c ^{recommended to all DC or combination (if gate or drains are tied together) of DC bias pads.}
For Individual Stage Bias -- Each DC pad (Vd1,2,3, Vss, and Vg1,2,3,4) needs to have DC bypass capacitance (~100-200 pF)
u ^{as close to the device as possible. Additional DC bypass capacitance (~0.01 uF) is also recommended.}
MTTF Tables (TBD)
d
These numbers were calculated based on accelerated life test information and thermal model analysis received from the fabricating foundry.
Backplate
Temperature
55 deg Celsius
Channel
Rth
Temperature
ro _{deg Celsius}
C/W
MTTF Hours
FITs
E+
E+
75 deg Celsius
deg Celsius
C/W
E+
E+
p _{95 deg Celsius}
deg Celsius
C/W
E+
E+
- _{Bias Conditions: Vd1=Vd2=Vd3=5.0V, Vss=-5.0V, Id1=230mA, Id2=140mA, Id3=75mA, Iss=50mA}
re
P
Mimix Broadband, Inc., 10795 Rockley Rd., Houston, Texas 77099
Tel: [phone] Fax: [phone] mimixbroadband.com
Page 6 of 9
Characteristic Data and Specifications are subject to change without notice. ©2005 Mimix Broadband, Inc.
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