AN9315: RF Amplifier Design Using HFA3046, HFA3096, HFA3127, HFA3128 Transistor Arrays

RF Amplifier Design Using HFA3046, HFA3096,
HFA3127, HFA3128 Transistor Arrays
TM
Application Note
November 1996
Introduction
AN9315.1
HFA3046
This application note is focused on exploiting the RF design
capabilities of HFA3046/3096/3127/3128 transistor arrays.
Detailed design procedures, using these transistor arrays,
for a matched (800MHz to 2500MHz) high-gain low-noise
amplifier and a 10MHz to 600MHz wideband feedback
amplifier are described.
1
2
Q1
Q5
3
4
1
TABLE 1. UHF-1 DEVICE CHARACTERISTIC
2
PNP
8
8
V
BVCBO, MIN
12
10
V
BVEBO, MIN
5.5
4.5
V
ICBO
0.1
0.1
nA
hFE
70
40
CCB
500
600
fF
9
5.5
GHz
P1DB (IC = 10mA, VCE = 5V,
fO = 1GHz)
7.6
6.2
dBm
IP3 (IC = 10mA, VCE = 5V,
fO = 1GHz)
17.6
16.2
dBm
NF (RS = 50Ω, IC = 5mA,
VCE = 3V, fO = 1GHz)
3.5
3.0
dB
10
Q1
3
Q2
Q5
6
7
8
Q3
Q4
12
Q4
8
11
10
7
8
Q3
14
13
Q2
Q3
HFA3127
4
15
Q5
6
9
7
16 NC
Q1
3
11
Q4
NC 5
fT
13
2
4
6
UNITS
BVCEO, MIN
1
5
The HFA3046, HFA3096, HFA3127, HFA3128 transistor
arrays are fabricated in a complementary bipolar bonded
wafer silicon-on-insulator (SOI) technology, dubbed UHF-1
[1]. All four products make use of the same die, which has
both NPN and PNP transistors on it. Figure 1 shows the
pinouts of the four different products. Typical NPN and PNP
transistor characteristics are shown in Table 1.
NPN
14
12
Q2
5
PARAMETERS
HFA3096
9
HFA3128
16
1
15
2
16
14
3
13
4
12
NC 5
12
11
6
11
10
7
9
8
Q1
15
14
Q2
Q5
13
10
Q3
Q4
9
FIGURE 1. PINOUTS OF HFA3046/3096/3127/3128 SOIC
PACKAGED TRANSISTOR ARRAYS
Circuit Design
High-Gain Low-Noise Amplifier
One important design requirement for an RF amplifier is the
accurate control of input and output impedance levels. This
is especially important if the amplifier is to interface with
matched source and load impedances.
Based on S-parameter measurements, for a common-emitter
configuration, transistors of HFA3127 exhibit a prematched
condition on the input side over a wide range of frequencies.
The package lead and bond wire inductances for these
transistors make the input impedance close to 50Ω. For
IC = 5mA - 10mA, VCE = 2V - 5V, the input VSWR of Q2 and
Q5 was less than -10dB for frequencies of 800MHz to
3000MHz. Furthermore, for these transistors, a good output
match, output VSWR < -10dB for frequencies 300MHz to
3000MHz, could be accomplished through bypassing the
collector with a 100Ω resistor. As the single stage amplifiers
built with Q2 and Q5 both show good input and output
matching, they can be cascaded for higher gain without
requiring an impedance transforming network. Figure 2 shows
the final two stage amplifier. The advantage of this circuit is its
simplicity. This design does not use any tuning inductors or
capacitors which would tend to increase the cost of the circuit.
Furthermore, this circuit accomplishes higher gain by
cascading two amplifier stages built with integrated transistors.
The SOI process has the advantage of lower DC and AC
parasitic leakage currents as opposed to junction isolation,
which leads to good isolation between transistors.
Furthermore, an SOI process provides substantially lower
collector to substrate capacitance, immunity to any possible
latch-up between the devices, and superior radiation
hardness.
The HFA3127 is used for the two stage matched (800MHz to
2500MHz) high-gain amplifier design, while the HFA3096 is
used for the 10MHz to 600MHz wideband feedback amplifier.
3-1
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Application Note 9315
0
-
R1
39kΩ
R2
100Ω
R3
39kΩ
R4
100Ω
C3 1nF
C2 1nF
Q5
Q2
RS
50Ω
–5
INPUT VSWR (dB)
VCC
+
VO
RL
50Ω
+VS
IC = 5mA, VCC = 3V
-10
–15
IC = 10mA, VCC = 5V
–20
FIGURE 2. HIGH-GAIN LOW-NOISE AMPLIFIER REALIZED
WITH HFA3127
From Figure 2, the noise figure of the whole circuit is mainly
controlled by the noise characteristics of the transistor Q5.
As shown in Figure 3D, this high-gain amplifier demonstrates
good noise performance. For IC2 = IC5 = 5mA, the measured
noise figure is 3.9dB at 900MHz, making this useful as a
high-gain, low-noise amplifier.
–25
0
1
2
3
FREQUENCY (GHz)
FIGURE 3B. INPUT VSWR
0
OUTPUT VSWR (dB)
Figure 3 shows the measured characteristics of the amplifier
under two different bias conditions: VCC = 3V, IC2 = IC5 =
5mA; and VCC = 5V, IC2 = IC5 = 10mA. As can be seen from
Figure 3, the input and output VSWR is less than -10dB for
frequencies greater than 800MHz. The amplifier shows better
performance at the expense of higher power dissipation (IC =
10mA and VCC = 5V) except the noise figure. For IC2 = IC5 =
10mA, the amplifier gains are 18.7, 8.8, and 6.6dB at
frequencies of 900MHz, 1800MHz, and 2200MHz,
respectively.
-5
-10
IC = 5mA, VCC = 3V
-15
IC = 10mA, VCC = 5V
-20
The complete microstrip board layout is shown in Figure 4. A
0.031 inch thick FR-4 (G-10) glass epoxy board is used for
the layout. The dielectric constant of the material is 4.7 at
1000MHz.
0
2
3
FREQUENCY (GHz)
FIGURE 3C. OUTPUT VSWR
40
6
NOISE FIGURE (dB)
30
GAIN (dB)
1
IC = 10mA, VCC = 5V
20
10
IC = 5mA, VCC = 3V
5
IC = 10mA, VCC = 5V
4
IC = 5mA, VCC = 3V
0
0
1
2
FREQUENCY (GHz)
FIGURE 3A. GAIN
3
3
0
0.5
1
FREQUENCY (GHz)
1.5
2
FIGURE 3D. NOISE
FIGURE 3. MEASURED CHARACTERISTICS OF THE HIGH
GAIN LOW-NOISE AMPLIFIER
3-2
Application Note 9315
Wideband Amplifier
OUTPUT
A well known simple amplifier configuration which achieves
flat gain and broadband matching without losing excessive
signal power is shown in Figure 6. The simultaneous use of
both shunt and series feedback gives rise to broadband
resistive input and output impedances [2, 3].
C3
THROUGH
HOLE
R4
CBP
HFA3127
R3
R1
C1
INPUT
C2
R2
CBP
Figure 7 shows a similar version of the double feedback
wideband amplifier circuit realized with the HFA3096. This
design takes advantage of the PNP transistors (Q4 and Q5)
available on the HFA3096, to bias amplifying transistor Q2
for good temperature stability.
RF
CBP
VO
RS
LCHOKE
+
-
VCC
FIGURE 4. MICROSTRIP BOARD LAYOUT FOR THE
HIGH-GAIN LOW-NOISE AMPLIFIER
The key rule for the circuit board layout is to make the
physical length of the conductors as short as possible where
the RF signal is involved. Although it seems obvious, it is
easy to forget that the impedance looking into a microstrip
line, that has load attached at the end, can be totally different
from the attached load impedance depending on the length
of the microstrip line and frequency. Outside the RF signal
path, it does not matter.
At RF frequencies, the value of chip resistors, capacitors,
and inductors should not be taken for granted. In general,
the smaller the size of the component, the better the
performance. However, it is important to evaluate the
components before use. For the RF frequencies, these
components can be evaluated easily using a network
analyzer by mounting them as shown in Figure 5. The SMA
connector itself contributes about 0.7pF of capacitance
between the signal and ground terminals.
CHIP COMPONENT
CUT CENTER
PINS FLUSH
TO FLANGE
SMA CONNECTOR
FIGURE 5. A CHIP COMPONENT MOUNTED ON AN SMA
CONNECTOR
3-3
VS
RL
RE
FIGURE 6. SINGLE STAGE SHUNT AND SERIES FEEDBACK
CIRCUIT
R4
100Ω
R1
2kΩ
Q5
Q4
R2
15kΩ
R3
1kΩ
RF
240Ω
+
5V
-
L1
1µH
C3
1nF
C1
1nF
VO
RL
50Ω
Q2
C2
1nF
RS
50Ω
RE
5.1Ω
+VS
FIGURE 7. WIDEBAND AMPLIFIER REALIZED WITH HFA3096
The frequency response of the wideband amplifier is shown
in Figure 8. As can be seen from Figure 8, the amplifier
shows 10dB of flat gain with 600MHz bandwidth.The input
and output matching is very good over the range of
frequency where gains are flat. The low frequency
performance is limited by the 1000pF capacitor.
The microstrip board layout for the wideband amplifier is
shown in Figure 9. A 0.031 inch thick FR-4 (G-10) glass
epoxy board is used for the layout.
Application Note 9315
0
15
-10
GAIN (dB)
VSWR (dB)
10
OUTPUT VSWR
-20
5
-30
INPUT VSWR
-40
0
107
108
FREQUENCY (Hz)
109
107
108
109
FREQUENCY (Hz)
FIGURE 8A. GAIN
FIGURE 8B. INPUT-OUTPUT VSWR
FIGURE 8. MEASURED CHARACTERISTICS OF THE WIDEBAND AMPLIFIER
Summary
A detailed process of designing a high-gain low-noise and a
wideband amplifier using the Intersil UHF transistor arrays is
summarized.
VCC
A two-stage, high-gain, low-noise amplifier built with the
HFA3127 demonstrates 50Ω input and output impedance
over a wide frequency range of 800MHz to 2500MHz without
the use of external matching networks. The gain at 900MHz
is in excess of 17dB with a noise figure of 3.9dB.
THROUGH
HOLE
LCHOKE
CBP
R1
R4
A wideband amplifier built with the HFA3096 demonstrates
excellent input and output matching with 10dB of constant
gain. The -3dB bandwidth of this amplifier is 600MHz. PNP
transistors available on the HFA3096 are used for
temperature stable biasing of the amplifying transistor.
R2
CBP
OUTPUT
L1
HFA3096
RE R
3
C1
C3
RF
CBP
C2
INPUT
FIGURE 9. MICROSTRIP BOARD LAYOUT FOR THE
WIDEBAND
References
[1] [1]C. Davis, et al, “UHF-1: A High Speed
Complementary Bipolar Analog Process on SOI,”
Proceeding of BCTM 92, pp260-263, Oct. 1992.
[2] [2]J. B. Couglin, et al, “A Monolithic Silicon wideband
Amplifier from DC to 1 GHz,” IEEE J. Solid-State
Circuits, vol. SC-8, pp414-419, Dec. 1973.
[3] [3]R. G. Meyer, et al, “A wideband Ultralinear Amplifier
from 3 to 300 MHz,” IEEE J. Solid-State Circuits, vol.
SC-9, pp167-175, Aug. 1974.
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Intersil semiconductor products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
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