XR1008-QB_15 Datasheet, PDF (4/7 Pages) M/A-COM Technology Solutions, Inc. – GaAs Receiver

37.0-40.0 GHz GaAs Receiver (USB)
SMT, 7x7 mm
April 2011 - Rev 27-Apr-11
Recommended Layout
R1008-QB
App Note [1] Biasing - Please refer to the functional block diagram and pin-out table for biasing information. The device is operated by
biasing VD=4.0V with ID=180 mA by adjusting the applied voltage on VG1. VG1 typically requires-0.5V to result in the drain current being
180mA. The nominal input impedance of this gate is 180Ohm, so it should be noted that the nominal gate current will be 2.7mA.
Additionally, a fixed bias of VG2=-0.5V is required to bias the mixer and doubler. Adjusting VG2 above or below this value can adversely affect
conversion gain, image rejection and intercept point performance. It is recommended to use active biasing to keep the currents constant as
the RF power and temperature vary; this gives the most reproducible results. The diagram “Active Bias Circuit” demonstrates a possible
method for active biasing. 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. 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
Active Bias Circuit
5.0V
5k76
4.0V
1
3.3V
MMBT3904
1
12k1
12k1
( ) I = 5-4
5.62
5R62 (sense)
4V, 180mA
4.0V
MMBT3906
100R
Vd
100n
10R
-5.0V
1k0
100n
3
BAV99
Vg1
3 ^BAV99
Mimix Broadband, Inc., 10795 Rockley Rd., Houston, Texas 77099
Tel: [phone] Fax: [phone] mimixbroadband.com
Page 4 of 7
Characteristic Data and Specifications are subject to change without notice. ©2011 Mimix Broadband, Inc.
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