Data Sheet HMC1126
Rev. B | Page 13 of 16
APPLICATIONS INFORMATION
The HMC1126 is a GaAs, pHEMT, MMIC, cascode distributed
power amplifier.
The cascode distributed amplifier uses a fundamental cell of
two FETs in series, source to drain. This fundamental cell then
duplicates a number of times. The major benefit of this is an
increase in the operation bandwidth. The basic schematic for a
fundamental cell is given in Figure 35.
13083-039
DD
V
GG
1
V
GG
2
RFOUT
RFIN
Figure 35. Fundamental Cell Schematic
The recommended bias sequence during power up is the
following:
1. Connect GND.
2. Set V
GG
1 to −2 V.
3. Set V
DD
to 5 V.
4. Set V
GG
2 to 1.4 V.
5. Increase V
GG
1 to achieve a typical quiescent current (I
DQ
) =
65 mA.
6. Apply the RF signal.
The recommended bias sequence during power down is the
following:
1. Turn of f the RF signal.
2. Decrease V
GG
1 to −2 V to achieve I
DQ
= 0 mA.
3. Decrease V
GG
2 to 0 V.
4. Decrease V
DD
to 0 V.
5. Increase V
GG
1 to 0 V.
MOUNTING AND BONDING TECHNIQUES FOR
MILLIMETERWAVE GaAs MMICS
Attach the die directly to the ground plane eutectically or with
conductive epoxy (see the Handling Precautions section, the
Mounting section, and the Wire Bonding section).
Microstrip, 50 Ω, transmission lines on 0.127 mm (5 mil) thick
alumina, thin film substrates are recommended for bringing the
radio frequency to and from the chip (see Figure 36). When using
0.254 mm (10 mil) thick alumina, thin film substrates, raise the
die 0.150 mm (6 mils) to ensure that the surface of the die is
coplanar with the surface of the substrate. One way to accomplish
this is to attach the 0.102 mm (4 mil) thick die to a 0.150 mm
(6 mil) thick, molybdenum (Mo) heat spreader (moly tab) which
can then be attached to the ground plane (see Figure 36 and
Figure 37).
RF GROUND PLANE
0.102mm (0.004") THICK GaAs MMIC
WIRE BOND
0.127mm (0.005") THICK ALUMINA
THIN FILM SUBSTRATE
0.076mm
(0.003")
13083-037
Figure 36. Die Without the Moly Tab
0.102mm (0.004") THICK GaAs MMIC
WIRE BOND
RF GROUND PLANE
0.254mm (0.010") THICK ALUMINA
THIN FILM SUBSTRATE
0.076mm
(0.003")
0.150mm (0.005") THICK
MOLY TAB
13083-038
Figure 37. Die With the Moly Tab
Place microstrip substrates as close to the die as possible to
minimize bond wire length. Typical die to substrate spacing is
0.076 mm to 0.152 mm (3 mil to 6 mil).
Handling Precautions
To avoid permanent damage, follow these storage, cleanliness,
static sensitivity, transient, and general handling precautions:
Place all bare die in either waffle or gel-based ESD
protective containers and then seal the die in an ESD
protective bag for shipment. Once the sealed ESD
protective bag is opened, store all die in a dry nitrogen
environment.
Handle the chips in a clean environment. Do not attempt
to clean the chip using liquid cleaning systems.
Follow ESD precautions to protect against ESD strikes.
While bias is applied, suppress instrument and bias supply
transients. Use shielded signal and bias cables to minimize
inductive pick up.
Handle the chip along the edges with a vacuum collet or
with a sharp pair of bent tweezers. The surface of the chip
may have fragile air bridges and must not be touched with
vacuum collet, tweezers, or fingers.
