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PDF HFA1245IP Data sheet ( Hoja de datos )
| Número de pieza | HFA1245IP | |
| Descripción | Dual/ 420MHz/ Low Power/ Video/ Current Feedback Operational Amplifier with Disable | |
| Fabricantes | Intersil Corporation | |
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Data Sheet
HFA1245
February 1999 File Number 3682.4
Dual, 420MHz, Low Power, Video, Current
Feedback Operational Amplifier with
Disable
The HFA1245 is a dual, high speed, low power current
feedback amplifier built with Intersil’s proprietary
complementary bipolar UHF-1 process.
The HFA1245 features individual TTL/CMOS compatible
disable controls. When pulled low they disable the
corresponding amplifier, which reduces the supply current
and forces the output into a high impedance state. This
feature allows easy implementation of simple, low power
video switching and routing systems. Component and
composite video systems also benefit from this op amp’s
excellent gain flatness, and good differential gain and phase
specifications.
Multiplexed A/D applications will also find the HFA1245
useful as the A/D driver/multiplexer.
The HFA1245 is a low power, high performance upgrade for
the popular Intersil HA5022. For a dual amplifier without
disable, in a standard 8 lead pinout, please see the HFA1205
data sheet.
Ordering Information
TEMP.
PART NUMBER RANGE (oC)
PACKAGE
PKG.
NO.
HFA1245IP
-40 to 85 14 Ld PDIP
E14.3
HA5022EVAL
High Speed Op Amp DIP Evaluation Board
Pinout
HFA1245
(PDIP)
TOP VIEW
-IN1 1
+IN1 2
DISABLE 1 3
V- 4
DISABLE 2 5
+IN2 6
-IN2 7
+-
+
-
14 OUT1
13 NC
12 GND
11 V+
10 NC
9 NC
8 OUT2
Features
• Low Supply Current . . . . . . . . . . . . . . . . . 5.8mA/Op Amp
• High Input Impedance . . . . . . . . . . . . . . . . . . . . . . . 2MΩ
• Low Crosstalk (5MHz) . . . . . . . . . . . . . . . . . . . . . . -83dB
• High Off Isolation (5MHz) . . . . . . . . . . . . . . . . . . . . . 65dB
• Wide -3dB Bandwidth (AV = +2) . . . . . . . . . . . . . . 420MHz
• Very Fast Slew Rate . . . . . . . . . . . . . . . . . . . . . . 1200V/µs
• Gain Flatness (to 50MHz) . . . . . . . . . . . . . . . . . . ±0.11dB
• Differential Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02%
• Differential Phase . . . . . . . . . . . . . . . . . . . . 0.03 Degrees
• Individual Output Enable/Disable
• Output Enable/Disable Time. . . . . . . . . . . . . . 150ns/30ns
• Pin Compatible Upgrade to HA5022
Applications
• Flash A/D Drivers
• High Resolution Monitors
• Video Multiplexers
• Video Switching and Routing
• Professional Video Processing
• Video Digitizing Boards/Systems
• Multimedia Systems
• RGB Preamps
• Medical Imaging
• Hand Held and Miniaturized RF Equipment
• Battery Powered Communications
• High Speed Oscilloscopes and Analyzers
1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Copyright © Intersil Corporation 1999
1 page  
HFA1245
Application Information
Relevant Application Notes
The following Application Notes pertain to the HFA1245:
• AN9787-An Intuitive Approach to Understanding
Current Feedback Amplifiers
• AN9420-Current Feedback Amplifier Theory and
Applications
• AN9663-Converting from Voltage Feedback to Current
Feedback Amplifiers
These publications may be obtained from Intersil’s web site
(http://www.intersil.com) or via our AnswerFAX system.
Optimum Feedback Resistor
Although a current feedback amplifier’s bandwidth
dependency on closed loop gain isn’t as severe as that of a
voltage feedback amplifier, there can be an appreciable
decrease in bandwidth at higher gains. This decrease may
be minimized by taking advantage of the current feedback
amplifier’s unique relationship between bandwidth and RF.
All current feedback amplifiers require a feedback resistor,
even for unity gain applications, and RF, in conjunction with
the internal compensation capacitor, sets the dominant pole
of the frequency response. Thus, the amplifier’s bandwidth is
inversely proportional to RF. The HFA1245 design is
optimized for a 750Ω RF at a gain of +2. Decreasing RF
decreases stability, resulting in excessive peaking and
overshoot (Note: Capacitive feedback will cause the same
problems due to the feedback impedance decrease at higher
frequencies). At higher gains the amplifier is more stable, so
RF can be decreased in a trade-off of stability for bandwidth.
The table below lists recommended RF values for various
gains, and the expected bandwidth. For good channel-to-
channel gain matching, it is recommended that all resistors
(termination as well as gain setting) be ±1% tolerance or
better. Note that a series input resistor, on +IN, is required for
a gain of +1, to reduce gain peaking and increase stability.
TABLE 1. OPTIMUM FEEDBACK RESISTOR
GAIN
(AV)
-1
RF (Ω)
475
BANDWIDTH
(MHz)
280
+1 560 (+RS = 650Ω)
+2 750
260
420
+5 200
270
+10 180
140
Channel-To-Channel Frequency Response Matching
The frequency response of channel 1 and channel 2 aren’t
perfectly matched. For the best channel-to-channel
frequency response match in a gain of 2 (see Figure 1), use
RF = 650Ω for channel 1 and RF = 806Ω for channel 2.
5
AV = +2
2
1 RF = 806Ω, CH2
0
-1
-2
RF = 650Ω, CH1
-3
-4
1 10 100
FREQUENCY (MHz)
FIGURE 1. CHANNEL 1 AND CHANNEL 2 MATCHED
FREQUENCY RESPONSE
1000
Non-inverting Input Source Impedance
For best operation, the DC source impedance seen by the
non-inverting input should be ≥50Ω. This is especially
important in inverting gain configurations where the
non-inverting input would normally be connected directly to
GND.
Pulse Undershoot and Asymmetrical Slew Rates
The HFA1245 utilizes a quasi-complementary output stage
to achieve high output current while minimizing quiescent
supply current. In this approach, a composite device
replaces the traditional PNP pulldown transistor. The
composite device switches modes after crossing 0V,
resulting in added distortion for signals swinging below
ground, and an increased undershoot on the negative
portion of the output waveform (see Figures 7, 11, 15, and
19). This undershoot isn’t present for small bipolar signals,
or large positive signals. Another artifact of the composite
device is asymmetrical slew rates for output signals with a
negative voltage component. The slew rate degrades as the
output signal crosses through 0V (see Figures 7, 11, 15, and
19), resulting in a slower overall negative slew rate. Positive
only signals have symmetrical slew rates as illustrated in the
large signal positive pulse response graphs (see Figures 5,
9, 13, and 17).
DISABLE Input TTL Compatibility
The HFA1245 derives an internal GND reference for the
digital circuitry as long as the power supplies are symmetrical
about GND. With symmetrical supplies the digital switching
threshold (VTH = (VIH + VIL)/2 = (2.0 + 0.8)/2) is 1.4V, which
ensures the TTL compatibility of the DISABLE input. If
asymmetrical supplies (e.g., +10V, 0V) are utilized, the
switching threshold becomes:
VTH = V-----+----2-+----V------ + 1.4V,
and the VIH and VIL levels will be VTH ±0.6V, respectively.
5 Page 
HFA1245
Typical Performance Curves VSUPPLY = ±5V, TA = 25oC, RF = Value From the Optimum Feedback Resistor Table, RL = 100Ω,
Unless Otherwise Specified (Continued)
VOUT = 200mVP-P
0.4
0.3
0.2
AV = +1, CH2
AV = +1, CH1
0.1
AV = +2, CH2
0
-0.1
AV = -1
-0.2
-0.3
-0.4
BOTH CHANNELS SHOWN
AV = +2, CH1
1 10
FREQUENCY (MHz)
100
FIGURE 28. GAIN FLATNESS
AV = +2, VIN = 1VP-P
-20
-30
-40
-50
-60
-70
-80
-90
-100
0.3 1
10 100
FREQUENCY (MHz)
1000
FIGURE 30. CROSSTALK (PASSIVE CHANNEL DISABLED)
10
20
30
40
50
60
70
80
90
100
1
AV = +2
AV = -1
AV = +1
10 100
FREQUENCY (MHz)
FIGURE 32. REVERSE ISOLATION
1000
11
AV = +2, VIN = 1VP-P
-20
-30
-40
-50
-60
-70
-80
-90
-100
0.3 1
10 100
FREQUENCY (MHz)
1000
FIGURE 29. CROSSTALK (PASSIVE CHANNEL ENABLED)
AV = +2, VIN = 1VP-P
20 DIS1 = DIS2 = 0V
30
40
50
60
70
80
90
100
0.3 1
10 100
FREQUENCY (MHz)
FIGURE 31. ALL HOSTILE OFF ISOLATION
1000
AV = +2
1K
100
10
1
0.1
0.01
0.3 1
10 100
FREQUENCY (MHz)
1000
FIGURE 33. ENABLED OUTPUT RESISTANCE
11 Page | ||
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| PDF Descargar | [ Datasheet HFA1245IP.PDF ] | |
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