Philips Semiconductors
Product specification
Wideband variable gain amplifier
SA5209
DESCRIPTION
The SA5209 represents a breakthrough in monolithic amplifier
design featuring several innovations. This unique design has
combined the advantages of a high speed bipolar process with the
proven Gilbert architecture.
The SA5209 is a linear broadband RF amplifier whose gain is
controlled by a single DC voltage. The amplifier runs off a single 5
volt supply and consumes only 40mA. The amplifier has high
impedance (1kΩ) differential inputs. The output is 50Ω differential.
Therefore, the 5209 can simultaneously perform AGC, impedance
transformation, and the balun functions.
The dynamic range is excellent over a wide range of gain setting.
Furthermore, the noise performance degrades at a comparatively
slow rate as the gain is reduced. This is an important feature when
building linear AGC systems.
PIN CONFIGURATION
N, D PACKAGES
V
CC1
GND
1
IN
A
GND
1
IN
B
GND
1
V
BG
V
AGC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
CC2
GND
2
OUT
A
GND
2
OUT
B
GND
2
GND
2
GND
2
SR00237
Figure 1. Pin Configuration
FEATURES
•
Gain to 1.5GHz
•
850MHz bandwidth
•
High impedance differential input
•
50Ω differential output
•
Single 5V power supply
•
0 - 1V gain control pin
•
>60dB gain control range at 200MHz
•
26dB maximum gain differential
•
Exceptional V
CONTROL
/ V
GAIN
linearity
•
7dB noise figure minimum
•
Full ESD protection
•
Easily cascadable
ORDERING INFORMATION
DESCRIPTION
16-Pin Plastic Small Outline (SO) package
16-Pin Plastic Dual In-Line Package (DIP)
APPLICATIONS
•
Linear AGC systems
•
Very linear AM modulator
•
RF balun
•
Cable TV multi-purpose amplifier
•
Fiber optic AGC
•
RADAR
•
User programmable fixed gain block
•
Video
•
Satellite receivers
•
Cellular communications
TEMPERATURE RANGE
-40 to +85°C
-40 to +85°C
ORDER CODE
SA5209D
SA5209N
DWG #
SOT109-1
SOT38-4
1997 Nov 07
2
853-1453 18663
Philips Semiconductors
Product specification
Wideband variable gain amplifier
SA5209
DC ELECTRICAL CHARACTERISTICS
T
A
= 25
o
C, V
CC1
= V
CC2
= +5.0V, V
AGC
= 1.0V, unless otherwise specified.
LIMITS
SYMBOL
R
BG
V
AGC
I
BAGC
PARAMETER
Bandgap loading
AGC DC control voltage range
AGC pin DC bias current
in
TEST CONDITIONS
Over temperature
1
Over temperature
1
0V<V
AGC
<1.3V
Over temperature
1
MIN
2
TYP
10
0-1.3
-0.7
-6
-10
MAX
UNIT
kΩ
V
µA
NOTES:
1. “Over Temperature Range” testing is as follows:
SA is -40 to +85°C
At the time of this data sheet release, the D package over-temperature data sheet limits are guaranteed via guardbanded room temperature
testing only.
AC ELECTRICAL CHARACTERISTICS
T
A
= 25
o
C, V
CC1
= V
CC2
= +5.0V, V
AGC
= 1.0V, unless otherwise specified.
LIMITS
SYMBOL
PARAMETER
TEST CONDITIONS
MIN
600
BW
-3dB bandwidth
Over temperature
1
DC - 500MHz
GF
V
IMAX
V
OMAX
NF
V
IN-EQ
S12
∆G/∆V
CC
∆G/∆T
C
IN
BW
AGC
P
O-1dB
P
I-1dB
IP3
OUT
IP3
IN
∆G
AB
Gain flatness
Maximum input voltage swing (single-ended) for
linear operation
2
Maximum output voltage swing (single-ended)
for linear operation
2
Noise figure (unmatched configuration)
Equivalent input noise voltage spectral density
Reverse isolation
Gain supply sensitivity (single-ended)
Gain temperature sensitivity
Input capacitance (single-ended)
-3dB bandwidth of gain control function
1dB gain compression point at output
1dB gain compression point at input
Third-order intercept point at output
Third-order intercept point at input
Gain match output A to output B
f = 100MHz
f = 100MHz, V
AGC
=0.1V
f = 100MHz, V
AGC
>0.5V
f = 100MHz, V
AGC
<0.5V
f = 100MHz, V
AGC
= 1V
R
L
= 50Ω
R
L
= 50Ω
R
L
= 1kΩ
R
S
= 50Ω, f = 50MHz
f = 100MHz
f = 100MHz
Over temperature
1
500
+0.4
+0.6
200
400
1.9
9.3
2.5
-60
0.3
0.013
2
20
-3
-10
+13
+5
0.1
dB
mV
P-P
mV
P-P
V
P-P
dB
nV/
√
Hz
dB
dB/V
dB/
°
C
pF
MHz
dBm
dBm
dBm
dBm
dB
TYP
850
MHz
MAX
UNIT
NOTE:
1. “Over Temperature Range” testing is as follows:
SA is -40 to +85°C
At the time of this data sheet release, the D package over-temperature data sheet limits are guaranteed via guardbanded room temperature
testing only.
2. With R
L
> 1kΩ, overload occurs at input for single-ended gain < 13dB and at output for single-ended gain > 13dB. With R
L
= 50Ω, overload
occurs at input for single-ended gain < 6dB and at output for single-ended gain > 6dB.
1997 Nov 07
4
Philips Semiconductors
Product specification
Wideband variable gain amplifier
SA5209
SA5209 APPLICATIONS
The SA5209 is a wideband variable gain amplifier (VGA) circuit
which finds many applications in the RF, IF and video signal
processing areas. This application note describes the operation of
the circuit and several applications of the VGA. The simplified
equivalent schematic of the VGA is shown in Figure 2. Transistors
Q1-Q6 form the wideband Gilbert multiplier input stage which is
biased by current source I1. The top differential pairs are biased
from a buffered and level-shifted signal derived from the V
AGC
input
and the RF input appears at the lower differential pair. The circuit
topology and layout offer low input noise and wide bandwidth. The
second stage is a differential transimpedance stage with current
feedback which maintains the wide bandwidth of the input stage.
The output stage is a pair of emitter followers with 50Ω output
impedance. There is also an on-chip bandgap reference with
buffered output at 1.3V, which can be used to derive the gain control
voltage.
Both the inputs and outputs should be capacitor coupled or DC
isolated from the signal sources and loads. Furthermore, the two
inputs should be DC isolated from each other and the two outputs
should likewise be DC isolated from each other. The SA5209 was
designed to provide optimum performance from a 5V power source.
However, there is some range around this value (4.5 - 7V) that can
be used.
The input impedance is about 1kΩ. The main advantage to a
differential input configuration is to provide the balun function.
Otherwise, there is an advantage to common mode rejection, a
specification that is not normally important to RF designs. The
source impedance can be chosen for two different performance
characteristics: Gain, or noise performance. Gain optimization will
be realized if the input impedance is matched to about 1kΩ. A 4:1
balun will provide such a broadband match from a 50Ω source.
Noise performance will be optimized if the input impedance is
matched to about 200Ω. A 2:1 balun will provide such a broadband
match from a 50Ω source. The minimum noise figure can then be
expected to be about 7dB. Maximum gain will be about 23dB for a
single-ended output. If the differential output is used and properly
matched, nearly 30dB can be realized. With gain optimization, the
noise figure will degrade to about 8dB. With no matching unit at the
input, a 9dB noise figure can be expected from a 50Ω source. If the
source is terminated, the noise figure will increase to about 15dB.
All these noise figures will occur at maximum gain.
The SA5209 has an excellent noise figure vs gain relationship. With
any VGA circuit, the noise performance will degrade with decreasing
V
CC
R
1
R
2
gain. The 5209 has about a 1.2dB noise figure degradation for
each 2dB gain reduction. With the input matched for optimum gain,
the 8dB noise figure at 23dB gain will degrade to about a 20dB
noise figure at 0dB gain.
The SA5209 also displays excellent linearity between voltage gain
and control voltage. Indeed, the relationship is of sufficient linearity
that high fidelity AM modulation is possible using the SA5209. A
maximum control voltage frequency of about 20MHz permits video
baseband sources for AM.
A stabilized bandgap reference voltage is made available on the
SA5209 (Pin 7). For fixed gain applications this voltage can be
resistor divided, and then fed to the gain control terminal (Pin 8).
Using the bandgap voltage reference for gain control produces very
stable gain characteristics over wide temperature ranges. The gain
setting resistors are not part of the RF signal path, and thus stray
capacitance here is not important.
The wide bandwidth and excellent gain control linearity make the
SA5209 VGA ideally suited for the automatic gain control (AGC)
function in RF and IF processing in cellular radio base stations,
Direct Broadcast Satellite (DBS) decoders, cable TV systems, fiber
optic receivers for wideband data and video, and other radio
communication applications. A typical AGC configuration using the
SA5209 is shown in Figure 3. Three SA5209s are cascaded with
appropriate AC coupling capacitors. The output of the final stage
drives the full-wave rectifier composed of two UHF Schottky diodes
BAT17 as shown. The diodes are biased by R1 and R2 to V
CC
such
that a quiescent current of about 2mA in each leg is achieved. An
SA5230 low voltage op amp is used as an integrator which drives
the V
AGC
pin on all three SA5209s. R3 and C3 filter the high
frequency ripple from the full-wave rectified signal. A voltage
divider is used to generate the reference for the non-inverting input
of the op amp at about 1.7V. Keeping D3 the same type as D1 and
D2 will provide a first order compensation for the change in Schottky
voltage over the operating temperature range and improve the AGC
performance. R6 is a variable resistor for adjustments to the op
amp reference voltage. In low cost and large volume applications
this could be replaced with a fixed resistor, which would result in a
slight loss of the AGC dynamic range. Cascading three SA5209s
will give a dynamic range in excess of 60dB.
The SA5209 is a very user-friendly part and will not oscillate in most
applications. However, in an application such as with gains in
excess of 60dB and bandwidth beyond 100MHz, good PC board
layout with proper supply decoupling is strongly recommended.
R
3
Q
7
A1
Q
8
Q
1
Q
2
Q
3
Q
4
R
4
I
2
OUT
B
OUT
A
50Ω
I
3
50Ω
V
AGC
0–1V
+
–
IN
B
Q
5
Q
6
BANDGAP
REFERENCE
I
1
IN
A
V
BG
SR00238
Figure 2. Equivalent Schematic of the VGA
1997 Nov 07
5
测试/测量
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