35.0-45.0 GHz GaAs Receiver

QFN, 7x7 mm

Page 4 of 7

R1008-QB

Mimix Broadband, Inc., 10795 Rockley Rd., Houston, Texas 77099

Tel: 281.988.4600 Fax: 281.988.4615 mimixbroadband.com

Characteristic Data and Specifications are subject to change without notice.

©2007 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.

March 2007 - Rev 21-Mar-07

Recommended Layout

Active Bias Circuit

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 180?, 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

5.0V

4V, 180mA

-5.0V

4.0V

Vd

Vg1

MMBT3906

1

5k76

12k1

12k1

MMBT3904

1

5R62 (sense)

100n

100R

1k0

BAV99

3

100n

BAV99

3

10R