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PDF SA5219 Data sheet ( Hoja de datos )
| Número de pieza | SA5219 | |
| Descripción | Wideband variable gain amplifier | |
| Fabricantes | Philips | |
| Logotipo |  |
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INTEGRATED CIRCUITS
SA5219
Wideband variable gain amplifier
Product specification
Replaces data of 1993 Dec 10
IC17 Data Handbook
1997 Nov 07
Philips Semiconductors
1 page  
Philips Semiconductors
Wideband variable gain amplifier
Product specification
SA5219
maximum control voltage frequency of about 20MHz permits video
baseband sources for AM.
A stabilized bandgap reference voltage is made available on the
SA5219 (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
SA5219 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
SA5219 is shown in Figure 3. Three SA5219s 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 VCC 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 VAGC pin on all three SA5219s. 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 SA5219s
will give a dynamic range in excess of 60dB.
The SA5219 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.
VAGC
0–1V
+
–
VCC
R1
Q1 Q2
R2
Q3 Q4
R3
A1
R4
Q7
Q8
50Ω
OUTB
I2 I3
OUTA
50Ω
INB Q5
INA
I1
Q6
BANDGAP
REFERENCE
Figure 2. Equivalent Schematic of VGA
VBG
SR00274
RF/IF
INPUT
5219
5219
5219
VCC
R1 R2
AGC
OUTPUT
R4 L1 L2
C4
–
5230
+
D1 D2
BAT 17
R3 C3
R6 D3
R5
BAT 17
VCC
Figure 3. AGC Configuration Using Cascaded SA5219s
SR00275
1997 Nov 07
5
5 Page 
Philips Semiconductors
Wideband variable gain amplifier
Product specification
SA5219
20
1.1V
0.8V
10
0.4V
200mV
0
100mV
–10 50mV
–20
–30
10
100
Frequency (MHz)
25mV
T = 25°C
RS = RL =
50Ω
Rt = 50Ω
See Test
Setup 1
1000 1500
SR00295
Figure 23. Insertion Gain vs Frequency and VAGC
15
5.5V
4.5V
10
5
T = 25°C
VAGC = 1.1V
0 RS = RL = 50Ω
Rt = 50Ω
See Test Setup 1
–5
10
100
Frequency (MHz)
1000 1500
SR00296
Figure 24. Insertion Gain vs Frequency and VCC
16
14
12 VCC = 7.0V
VCC = 6.0V
VCC = 5.0V
10 VCC = 4.5V
8
T = 25°C
6 VAGC = 1.1V
Rt = 50Ω
f = 10MHz
4 See Test Setup 1
2
0
–100
–50
0
50 100 150
Temperature (°C)
SR00297
Figure 25. Insertion Gain vs Temperature and VCC
0
–5
–10
125°C
–15
25°C
-55°C
–20
RS = RL = 50Ω
Rt = 50Ω
See Test Setup 1
–25
10
100
Frequency (MHz)
1000 1500
SR00298
Figure 26. Output Return Loss vs Frequency
1997 Nov 07
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet SA5219.PDF ] | |
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