(V ) and a single negative gate
a good input/output port match.
Applications
DD
supply (V ). The recommended
G1
The TC724 series of traveling
wave amplifiers are designed
for use as general purpose wide-
band power stages in communi-
cation systems and microwave
instrumentation. They are ideal-
ly suited for broadband applica-
tions requiring high output
power and excellent port match-
es over a 2 to 26.5 GHz frequen-
cy range. Dynamic gain control
and low-frequency extension ca-
pabilities are designed into
these devices.
Assembly Techniques
bias conditions for the TC724
are V = 11.0V, I = 400mA.
Solder die–attach using a flux-
less AuSu solder preform is the
recommended assembly meth-
od. Gold thermosonic wedge
bonding with 0.7 mil diameter
Au wire is recommended for all
bonds. Tool force should be 22
± 1gram, stage temperature
should be 150 ± 2°C and ultra-
sonic power and duration
DD
DD
To achieve this drain current
level, V is typically biased be-
G1
tween –0.3V and –1.0V. No other
bias supplies or connections to
the device are required for 2 to
26.5 GHz operation. The gate
voltage (V ) MUST be applied
G1
prior to the drain voltage (V
)
DD
during power up and removed
after the drain voltage during
power down. See Figure 3 for
assembly information.
should be 64 ±1 dB and 76 ±8
msec, respectively. The bonding
pad and chip backside metalli-
zation is gold.
It is characteristic of traveling
wave amplifiers that S tends
The auxiliary gate and drain
22
contacts are used only for low-
frequency performance exten-
sion below ≈ 1.0 GHz. When
used, these contacts must be AC
coupled only. (Do not attempt to
apply bias to these pads.)
Agilent application note #54,
"GaAs MMIC ESD, Die Attach
and Bonding Guidelines" pro-
vides basic information on these
subjects.
to 0dB and greater out of band.
This is the design trade–off for
the broadband performance of
TWAs. As a consequence, TWAs
are not necessarily uncondition-
ally stable out of band. This
means that if a TWA is followed
by a reflective low–pass filter,
oscillations can occur. This phe-
nomenon is exacerbated by low
temperature where the gain is
higher. More data will follow on
individual devices.
Additional References:
AN #56, “GaAs MMIC TWA Us-
ers Guide.”
The second gate (V ) can be
G2
used to obtain 30 dB (typical)
dynamic gain control. For nor-
mal operation, no external bias
is required on this contact and
its self-bias potential is + 2.0
volts. Applying an external bias
between its open circuit poten-
tial and a negative voltage of no
Biasing and Operation
These amplifiers are biased with
a single positive drain supply
less than (V –12) volts will ad-
DD
just the gain while maintaining
Seven Identical Stages
Drain Bias
(VDD)
• • •
RF Output
48
TC724
Rdam
2.7K
7.5
9.2
15
• • •
Aux. Drain
RF Input
Cg2
410pH
3.5
Aux.
Second Gate
24.2K
• • •
• • •
7.5
5.0
Bias (V )
G2
9.0K Cg1
48
9.4
1160
Aux. Gate
Parameter Value Table[1]
Single Stage
Shown
Temp. Diode
First Gate
Bias (VG1
Sense
)
Stage
Cg1
Cg2
(pF)
3.5
Rdamp
(pF)
1130
470
376
417
470
496
391
Temp. Diode
Force
Extra First Gate
Force
No.
(fF)
Bias (VG1
)
1
147
2
3
4
5
6
7
163
181
214
240
280
327
5.5
5.5
5.5
5.5
5.5
5.9
Notes:
Figure 1.
TC724 Schematic
•
•
All FETs have 390 micron gate periphery.
All Resistors in ohms (W)
(or in K–ohms, where indicated).
All capacitors in pico–farads (pF),
or in femto-farads, where indicated.
•
1. Damping circuit topology has been approximated by
these values.
TC724/rev.3.3
3
AGILENT [ AGILENT TECHNOLOGIES, LTD. ]
