TQ9147B 查看數據表（PDF） - TriQuint Semiconductor
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TQ9147B Datasheet PDF : 10 Pages
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Product Description
The TQ9147 is a high efficiency two stage GaAs MESFET
power amplifier IC intended for use in AMPS (IS-19)
applications that operate in the US Cellular (824 - 849 MHz)
band. The TQ9147 requires minimal external RF circuitry and
operates from a 4.8-Volt supply. With its flexible, off-chip, single
component output matching circuit, the TQ9147 is suitable for
use in other applications near the cellular band, such as 900
MHz ISM applications.
The TQ9147 utilizes a space saving SO-16 plastic package that
minimizes board area and cost.
Operation
Please refer to the application circuit above.
Gate Biasing and Bypassing
The TQ9147 is a dual-supply power amplifier (PA). Because it
utilizes depletion-mode MESFETs, a negative bias voltage must
be supplied to the gate of each FET. There are several
excellent choices of negative voltage bias supplies (charge
pumps) on the market, such as the Maxim MAX881R, or the
Harris ILC7660S. A simple resistor divider circuit is the most
inexpensive way to bias the gates of each stage from the charge
pump. However, due to fabrication tolerances and the large
window of main supply voltages under which the device can
function, the active bias method shown in the application circuit
is recommended.
This bias technique accurately sets the bias point for each stage
and optimizes the quiescent current and efficiency over a wide
range of supply voltages and output power levels. The following
table lists the nominal values of gate voltage and quiescent
current when this bias method is used. It is important to
remember that the negative gate voltage must be supplied first
in order to protect the device from inadvertent high drain
currents. If the drains are turned on before the gate bias is set,
the IC can be damaged or destroyed.
TQ9147B
Data Sheet
Gate Bias Voltages and Drain Quiescent Current
Parameter
VDD
VG1
VG2
IDQ1
IDQ2
Value
4.8
-1.5
-2.2
50
0-100
Units
V
V
V
MA
mA
The gate of each FET in the IC is RF bypassed on chip.
However, additional low frequency filtering and noise
suppression must be done externally. This is accomplished with
a 51 Ohm resistor (R1) and 0.1 µF cap (C4) from pin 11 (Vg2).
This capacitor and resistor combination also ensures device
stability under all conditions.
Drain Bypassing
C1 (0.1 µF) provides RF bypassing for the high impedance side
of the RF choke (L1).
Input Match
The device input is internally matched to 50 Ohms. A 50-Ohm
transmission line is all that is required between the PA and the
driver amp.
Output Match and High Power Bias Injection
Pins 1 and 16 are dual-purpose pins, providing for both the RF
output and the high power DC input for the drain of the second
stage FET. As such, these pins are connected to a 50-Ohm
transmission line. Locating C2 (8.2 pF) approximately 200 mils
from the device along this transmission line acts as a shorted
stub tuner that transforms the low output impedance (~ 7.5
Ohms) of the power stage to 50 Ohms. Varying the position of
C2 along the line can alter the output match in order to optimize
either power output or efficiency. In general, the farther away
C2 is from the pins the higher the efficiency at the expense of
power output. The closer the cap is, the higher the output
power at the expense of efficiency. By varying the value and
position of C2, the device can be easily tuned for a different
frequency range such as the 902 – 928 MHz ISM band. C3 (68
pF) is a DC blocking cap.
For additional information and latest specifications, see our website: www.triquint.com
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