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PDF AD816 Data sheet ( Hoja de datos )
| Número de pieza | AD816 | |
| Descripción | 500 mA Differential Driver and Dual Low Noise VF Amplifiers | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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a
500 mA Differential Driver and
Dual Low Noise (VF) Amplifiers
AD816*
FEATURES
Flexible Configuration
Two Low Noise Voltage Feedback Amplifiers with
High Current Drive, Ideal for ADSL Receivers or
Drivers for Low Impedance Loads such as CRT Coils
Two High Current Drive Amplifiers, Ideal for an ADSL
Differential Driver or Single Ended Drivers for Low
Impedance Loads such as CRT Coils
Thermal Overload Protection
CURRENT FEEDBACK AMPLIFIERS/DRIVERS
High Output Drive
26 dBm Differential Line Drive for ADSL Transmitters
40 V p-p Differential Output Voltage, RL = 50 ⍀ @ 1 MHz
500 mA Continuous Current, RL = 5 ⍀
1 A Peak Current, 1% Duty Cycle, RL = 15 ⍀ for DMT
Low Distortion
–68 dB @ 1 MHz THD, RL = 100 ⍀, VO = 40 V p-p
High Speed
120 MHz Bandwidth (–3 dB)
1500 V/s Differential Slew Rate, VO = 10 V p-p, G = +5
70 ns Settling Time to 0.1%
VOLTAGE FEEDBACK AMPLIFIERS/RECEIVERS
High Input Performance
4 nV/√Hz Voltage Noise
15 mV Max Input Offset Voltage
Low Distortion
–68 dB @ 1 MHz THD, VO = 10 V p-p, RL = 200 ⍀
High Speed
100 MHz Bandwidth (–3 dB)
180 V/s Slew Rate
High Output Drive
70 mA Output Current Drive
APPLICATIONS
ADSL, VDSL and HDSL Line Interface Driver and Receiver
CRT Convergence and Astigmatism Adjustment
Coil and Transformer Drivers
Composite Audio Amplifiers
PRODUCT DESCRIPTION
The AD816 consists of two high current drive and two low
noise amplifiers. These can be configured differentially for driv-
ing low impedance loads and receiving signals over twisted pair
cable or could be used independently for single ended driving
application such as correction circuits within high resolution
CRT Monitors.
FUNCTIONAL BLOCK DIAGRAM
TAB IS
+VS
15
14
13
12
11
B 10
9
+VS 8
–VS 7
6
A5
4
3
2
1
NC = NO CONNECT
NC
OUT2 RECEIVER
–IN2 RECEIVER
+IN2 RECEIVER
+IN2 DRIVER
–IN2 DRIVER
OUT2 DRIVER
+VS
–VS
OUT1 DRIVER
–IN1 DRIVER
+IN1 DRIVER
+IN1 RECEIVER
–IN1 RECEIVER
OUT1 RECEIVER
The two high output drive amplifiers are capable of supplying
a minimum of 500 mA continuous output current and up to
1A peak output current, and when configured differentially,
40 V p-p differential output swing can be achieved on ± 15 V
supplies into a load of 50 Ω. The drivers have 120 MHz of
bandwidth and 1,500 V/µs of differential slew rate while
featuring total harmonic distortion of –68 dB at 1 MHz into a
100 Ω load, specifications required for high frequency telecom-
munication subscriber line drivers.
The low noise voltage feedback amplifiers are fully independent
and can be configured differentially for use as receiver amplifi-
ers within a subscriber line hybrid interface or individually for
signal conditioning or filtering. The low noise of 4 nV/√Hz and
distortion of –68 dB at 1 MHz enable low level signals to be
resolved and amplified in the presence of large common-mode
voltages. 100 MHz of bandwidth and 180 V/µs of slew rate
combined with a load drive capability of 70 mA enable these
amplifiers to drive passive filters and low inductance coils. The
AD816 has thermal overload protection for system reliability
and is available in low thermal resistance power packages. The
AD816 operates over the industrial temperature range (–40°C
to +85°C).
REV. B
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1999
1 page  
Typical Driver Performance Characteristics–AD816
30 60 60
VS = ؎15V
–IB, VS = ؎15V
25 50 50
20 40 40
15 30
10 20
VS = ؎5V
5 10
00
10 100 1k 10k
LOAD RESISTANCE – (Differential – ⍀) (Single-Ended – ⍀/2)
Figure 2. Driver Output Voltage Swing vs. Load Resistance
30
–IB, VS = ؎5V
20
10
+IB, VS = ؎5V, ؎15V
0
–40 –20 0
20 40
60 80
JUNCTION TEMPERATURE – ؇C
100
Figure 5. Driver Input Bias Current vs. Temperature
100 100
INVERTING INPUT
CURRENT NOISE
10 10
NONINVERTING INPUT
CURRENT NOISE
INPUT VOLTAGE
1 NOISE
1
10 100 1k 10k 100k
FREQUENCY – Hz
Figure 3. Driver Input Current and Voltage Noise vs.
Frequency
–40
VS = ؎15V
–50 G = +10
VOUT = 40V p-p
–60
–70 RL = 50⍀
(DIFFERENTIAL)
–80
–90
–100
50⍀
100⍀
400⍀
RL = 200⍀
(DIFFERENTIAL)
–110
100
1k 10k 100k 1M 10M
FREQUENCY – Hz
Figure 6. Driver Total Harmonic Distortion vs. Frequency
0
–10 VS = ؎15V
G = +2
–20 RL = 100⍀
–30
–40
–PSRR
–50
+PSRR
–60
–70
–80
–90
–100
0.01
0.1 1 10
FREQUENCY – MHz
100 300
Figure 4. Driver Power Supply Rejection vs. Frequency
80
70 VS = ؎15V
60
50
40
VIN
30
20
1k⍀
1k⍀
1k⍀
1k⍀
VOUT
10
10k
100k
1M
10M
FREQUENCY – Hz
100M
Figure 7. Driver Common-Mode Rejection vs. Frequency
REV. B
–5–
5 Page 
AD816
THEORY OF OPERATION (DRIVER)
The AD816 driver is a dual current feedback amplifier with high
(500 mA) output current capability. Being a current feedback
amplifier, the AD816 driver’s open-loop behavior is expressed
as transimpedance, ∆VO/∆I–IN, or TZ. The open-loop trans-
impedance behaves just as the open-loop voltage gain of a volt-
age feedback amplifier, that is, it has a large dc value and de-
creases at roughly 6 dB/octave in frequency.
Since RIN is proportional to 1/gM, the equivalent voltage gain is
just TZ × gM, where the gM in question is the transconductance
of the input stage. Figure 42 shows the driver connected as a
follower with gain. Basic analysis yields the following results:
( )VO = G ×
TZ S
( )VIN TZ S + G × RIN + RF
where:
G=
1 + RF
RG
RIN = 1/gM ≈ 25 Ω
RG
RN
RF
RIN
VOUT
VIN
Figure 42. Current-Feedback Amplifier Operation
Recognizing that G × RIN << RF for low gains, it can be seen to
the first order that bandwidth for this amplifier is independent
of gain (G).
Considering that additional poles contribute excess phase at
high frequencies, there is a minimum feedback resistance below
which peaking or oscillation may result. This fact is used to
determine the optimum feedback resistance, RF. In practice
parasitic capacitance at the inverting input terminal will also add
phase in the feedback loop so that picking an optimum value for
RF can be difficult.
Achieving and maintaining gain flatness of better than 0.1 dB at
frequencies above 10 MHz requires careful consideration of
several issues.
Choice of Feedback and Gain Resistors
The fine scale gain flatness will, to some extent, vary with
feedback resistance. It is therefore recommended that once
optimum resistor values have been determined, 1% tolerance
values should be used if it is desired to maintain flatness over a
wide range of production lots. Table I shows optimum values
for several useful gain configurations. These should be used as a
starting point in any application.
Table I. Driver Resistor Values
G = +1
–1
+2
+5
+10
RF (⍀)
604
499
499
499
1k
RG (⍀)
∞
499
499
125
110
DRIVER DC ERRORS AND NOISE
There are three major noise and offset terms to consider in a
current feedback amplifier. For offset errors refer to the equa-
tion below. For noise error the terms are root-sum-squared to
give a net output error. In the circuit below (Figure 43), they
are input offset (VIO) which appears at the output multiplied by
the noise gain of the circuit (1 + RF/RG), noninverting input
current (IBN × RN) also multiplied by the noise gain, and the
inverting input current, which when divided between RF and RG
and subsequently multiplied by the noise gain always appear at
the output as IBI × RF. The input voltage noise of the AD816 is
less than 4 nV/√Hz. At low gains, however, the inverting input
current noise times RF is the dominant noise source. Careful
layout and device matching contribute to better offset and drift.
The typical performance curves in conjunction with the equations
below can be used to predict the performance of the AD816 in
any application.
VOUT
= VIO 1 +
RF
RG
±
I BN
RN
1
+
RF
RG
±
I BI
RF
RG
RN VIO
RF
IBI
AD816
IBN DRIVERS
VOUT
Figure 43. Driver Output Offset Voltage
THEORY OF OPERATION (RECEIVER)
Each AD816 receiver is a wide band high performance opera-
tional amplifier. It also provides a constant slew rate, bandwidth
and settling time over its entire specified temperature range.
The AD816 receiver consists of a degenerated NPN differential
pair driving matched PNPs in a folded-cascode gain stage. The
output buffer stage employs emitter followers in a class AB
amplifier which deliver the necessary current to the load while
maintaining low levels of distortion.
A protection resistor in series with the noninverting input is
required in circuits where the input to the receiver could be
subject to transients on continuous overload voltages exceeding
the ± 6 V maximum differential limit. The resistor provides
protection for the input transistors, by limiting their maximum
base current.
REV. B
–11–
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AD816.PDF ] | |
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