Biasing and Operation
The recommended quiescent DC bias condition for op-
timum efficiency, performance, and reliability is Vd=5.5
volts with Vg set for Id=800 mA. Minor improvements in
performance are possible depending on the application.
The drain bias voltage range is 3 to 5.5V. A single DC gate
supply connected to Vg will bias all gain stages. Muting
can be accomplished by setting Vg to the pinch-off volt-
age Vp (-1.0V).
An optional output power detector network is also
provided. The differential voltage between the Det-Ref
and Det-Out pads can be correlated with the RF power
emerging from the RF output port. The detected voltage
is given by :
V
=
(
ref
−
V
det
)
−
V
ofs
V
Assembly Techniques
The backside of the MMIC chip is RF ground. For microstrip
applications the chip should be attached directly to the
ground plane (e.g. circuit carrier or heatsink) using electri-
cally conductive epoxy [1]
For best performance, the topside of the MMIC should be
brought up to the same height as the circuit surrounding
it. This can be accomplished by mounting a gold plate
metal shim (same length and width as the MMIC) under
the chip which is of correct thickness to make the chip
and adjacent circuit the same height. The amount of
epoxy used for the chip and/or shim attachment should
be just enough to provide a thin fillet around the bottom
perimeter of the chip or shim. The ground plain should
be free of any residue that may jeopardize electrical or
mechanical attachment.
where
V
ref
is the voltage at the
DET
_
R
port,
V
det
is a voltage
The location of the RF bond pads is shown in Figure 12.
at the
DET
_
O
port, and
V
ofs
is the zero-input-power offset
Note that all the RF input and output ports are in a Ground-
voltage. There are three methods to calculate :
Signal-Ground configuration.
V
ofs
can be measured before each detector measure-
1.
RF connections should be kept as short as reasonable to
ment (by removing or switching off the power source
minimize performance degradation due to undesirable
and measuring ). This method gives an error due to
series inductance. A single bond wire is normally sufficient
temperature drift of less than 0.01dB/50°C.
for signal connections, however double bonding with 0.7
V
ofs
can be measured at a single reference temperature.
2.
mil gold wire or use of gold mesh [2] is recommended
The drift error will be less than 0.25dB.
for best performance, especially near the high end of the
3.
V
ofs
can either be characterized over temperature and frequency band.
stored in a lookup table, or it can be measured at two Thermosonic wedge bonding is preferred method for wire
temperatures and a linear fit used to calculate at any attachment to the bond pads. Gold mesh can be attached
temperature. This method gives an error close to the using a 2 mil round tracking tool and a tool force of ap-
method #1.
proximately 22 grams and a ultrasonic power of roughly
The RF ports are AC coupled at the RF input to the first stage
and the RF output of the final stage. No ground wires are
needed since ground connections are made with plated
through-holes to the backside of the device.
55 dB for a duration of 76 +/- 8 mS. The guided wedge at
an untrasonic power level of 64 dB can be used for 0.7 mil
wire. The recommended wire bond stage temperature is
150 +/- 2C.
Caution should be taken to not exceed the Absolute Maxi-
mum Rating for assembly temperature and time.
The chip is 100um thick and should be handled with care.
This MMIC has exposed air bridges on the top surface and
should be handled by the edges or with a custom collet
(do not pick up the die with a vacuum on die center).
This MMIC is also static sensitive and ESD precautions
should be taken.
Notes:
[1] Ablebond 84-1 LM1 silver epoxy is recommended.
[2] Buckbee-Mears Corporation, St. Paul, MN, 800-262-3824
5
AVAGO [ AVAGO TECHNOLOGIES LIMITED ]
