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PDF AD828 Data sheet ( Hoja de datos )
| Número de pieza | AD828 | |
| Descripción | Low Power Video Op Amp | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de AD828 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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a
Dual, Low Power
Video Op Amp
AD828
FEATURES
Excellent Video Performance
Differential Gain and Phase Error of 0.01% and 0.05؇
High Speed
130 MHz 3 dB Bandwidth (G = +2)
450 V/s Slew Rate
80 ns Settling Time to 0.01%
Low Power
15 mA Max Power Supply Current
High Output Drive Capability
50 mA Minimum Output Current per Amplifier
Ideal for Driving Back Terminated Cables
Flexible Power Supply
Specified for +5 V, ؎5 V, and ؎15 V Operation
؎3.2 V Min Output Swing into a 150 ⍀ Load
(VS = ؎5 V)
Excellent DC Performance
2.0 mV Input Offset Voltage
Available in 8-Lead SOIC and 8-Lead Plastic Mini-DIP
FUNCTIONAL BLOCK DIAGRAM
OUT1 1
–IN1 2
+IN1 3
V– 4
AD828
8 V+
7 OUT2
6 –IN2
5 +IN2
GENERAL DESCRIPTION
The AD828 is a low cost, dual video op amp optimized for use
in video applications that require gains of +2 or greater and
high output drive capability, such as cable driving. Due to its
low power and single-supply functionality, along with excellent
differential gain and phase errors, the AD828 is ideal for power-
sensitive applications such as video cameras and professional
video equipment.
With video specs like 0.1 dB flatness to 40 MHz and low
differential gain and phase errors of 0.01% and 0.05°, along
with 50 mA of output current per amplifier, the AD828 is an
excellent choice for any video application. The 130 MHz gain
bandwidth and 450 V/µs slew rate make the AD828 useful in
many high speed applications, including video monitors, CATV,
color copiers, image scanners, and fax machines.
+V 0.1F
VIN
RT
75⍀
1/2
AD828
RBT
75⍀
75⍀
RT
0.1F
75⍀
1k⍀
–V
1k⍀
The AD828 is fully specified for operation with a single 5 V
power supply and with dual supplies from ± 5 V to ± 15 V. This
power supply flexibility, coupled with a very low supply current
of 15 mA and excellent ac characteristics under all power supply
conditions, make the AD828 the ideal choice for many demand-
ing yet power-sensitive applications.
The AD828 is a voltage feedback op amp that excels as a gain
stage (gains > +2) or active filter in high speed and video systems
and achieves a settling time of 45 ns to 0.1%, with a low input
offset voltage of 2 mV max.
The AD828 is available in low cost, small 8-lead plastic mini-DIP
and SOIC packages.
0.03
DIFF GAIN
0.02
0.07 0.01
0.06
DIFF PHASE
0.05
Figure 1. Video Line Driver
REV. C
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
0.04
5
10
SUPPLY VOLTAGE – ؎V
15
Figure 2. Differential Phase vs. Supply Voltage
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2002
1 page  
AD828—Typical Performance Characteristics
20 7.7
15
+VCM
10
–VCM
5
0
0 5 10 15 20
SUPPLY VOLTAGE – ؎V
TPC 1. Common-Mode Voltage Range vs. Supply
Voltage
20
15
RL = 500⍀
10
RL = 150⍀
5
0
0 5 10 15 20
SUPPLY VOLTAGE – ؎V
TPC 2. Output Voltage Swing vs. Supply Voltage
7.2
+85؇C
+25؇C
6.7
–40؇C
6.2
5.7
0
5 10 15
SUPPLY VOLTAGE – ؎V
20
TPC 4. Quiescent Supply Current per Amp vs. Supply
Voltage for Various Temperatures
500
450
400
350
300
0
5 10
SUPPLY VOLTAGE – ؎V
15
TPC 5. Slew Rate vs. Supply Voltage
20
30
25
Vs = ؎15V
20
15
10
Vs = ؎5V
5
0
10 100
1k 10k
LOAD RESISTANCE – ⍀
TPC 3. Output Voltage Swing vs. Load Resistance
100
10
1
0.1
0.01
1k
10k
100k
1M
10M 100M
FREQUENCY – Hz
TPC 6. Closed-Loop Output Impedance vs. Frequency
–4– REV. C
5 Page 
AD828
THEORY OF OPERATION
The AD828 is a low cost, dual video operational amplifier
designed to excel in high performance, high output current
video applications.
The AD828 consists of a degenerated NPN differential pair
driving matched PNPs in a folded-cascade gain stage (Figure 4).
The output buffer stage employs emitter followers in a class AB
amplifier that delivers the necessary current to the load while
maintaining low levels of distortion.
The AD828 will drive terminated cables and capacitive loads of
10 pF or less. As the closed-loop gain is increased, the AD828
will drive heavier cap loads without oscillating.
+VS
OUTPUT
–IN
+IN
Figure 4. Simplified Schematic
–VS
INPUT CONSIDERATIONS
An input protection resistor (RIN in TPC 31) is required in circuits
where the input to the AD828 will be subjected to transient or
continuous overload voltages exceeding the ± 6 V maximum dif-
ferential limit. This resistor provides protection for the input
transistors by limiting their maximum base current.
For high performance circuits, the “balancing” resistor should be
used to reduce the offset errors caused by bias current flowing
through the input and feedback resistors. The balancing resistor
equals the parallel combination of RIN and RF and thus provides
a matched impedance at each input terminal. The offset voltage
error will then be reduced by more than an order of magnitude.
APPLYING THE AD828
The AD828 is a breakthrough dual amp that delivers precision and
speed at low cost with low power consumption. The AD828 offers
excellent static and dynamic matching characteristics, combined
with the ability to drive heavy resistive loads.
As with all high frequency circuits, care should be taken to main-
tain overall device performance as well as their matching. The
following items are presented as general design considerations.
Circuit Board Layout
Input and output runs should be laid out so as to physically
isolate them from remaining runs. In addition, the feedback
resistor of each amplifier should be placed away from the feed-
back resistor of the other amplifier, since this greatly reduces
interamp coupling.
Choosing Feedback and Gain Resistors
To prevent the stray capacitance present at each amplifier’s
summing junction from limiting its performance, the feedback
resistors should be ≤ 1 kΩ. Since the summing junction capaci-
tance may cause peaking, a small capacitor (1 pF to 5 pF) may
be paralleled with RF to neutralize this effect. Finally, sockets
should be avoided, because of their tendency to increase interlead
capacitance.
Power Supply Bypassing
Proper power supply decoupling is critical to preserve the
integrity of high frequency signals. In carefully laid out designs,
decoupling capacitors should be placed in close proximity to
the supply pins, while their lead lengths should be kept to a
minimum. These measures greatly reduce undesired inductive
effects on the amplifier’s response.
Though two 0.1 µF capacitors will typically be effective in
decoupling the supplies, several capacitors of different values
can be paralleled to cover a wider frequency range.
PARALLEL AMPS PROVIDE 100 mA TO LOAD
By taking advantage of the superior matching characteristics of the
AD828, enhanced performance can easily be achieved by employ-
ing the circuit in Figure 5. Here, two identical cells are paralleled
to obtain even higher load driving capability than that of a single
amplifier (100 mA min guaranteed). R1 and R2 are included to
limit current flow between amplifier outputs that would arise in
the presence of any residual mismatch.
1k⍀
VIN
1k⍀
1k⍀ +VS
1F
0.1F
28
1/2
AD828
3
1
5
1/2
AD828 7
6 4 0.1F
1F
R1
5⍀
R2
5⍀
VOUT
RL
1k⍀ –VS
Figure 5. Parallel Amp Configuration
–10–
REV. C
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet AD828.PDF ] | |
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