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PDF LMH672 Data sheet ( Hoja de datos )
| Número de pieza | LMH672 | |
| Descripción | Wideband Video Op Amp; Single / Single with Shutdown and Quad | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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March 2003
LMH6714/6720/6722
Wideband Video Op Amp; Single, Single with Shutdown
and Quad
General Description
The LMH6714/6720/6722 series combine National’s
VIP10™ high speed complementary bipolar process with
National’s current feedback topology to produce a very high
speed op amp. These amplifiers provide a 400MHz small
signal bandwidth at a gain of +2V/V and a 1800V/µs slew
rate while consuming only 5.6mA from ±5V supplies.
The LMH6714/6720/6722 series offer exceptional video per-
formance with its 0.01% and 0.01˚ differential gain and
phase errors for NTSC and PAL video signals while driving a
back terminated 75Ω load. They also offer a flat gain re-
sponse of 0.1dB to 120MHz. Additionally, they can deliver
70mA continuous output current. This level of performance
makes them an ideal op amp for broadcast quality video
systems.
The LMH6714/6720/6722’s small packages (SOIC &
SOT23), low power requirement, low noise and distortion
allow the LMH6714/6720/6722 to serve portable RF applica-
tions. The high impedance state during shutdown makes the
LMH6720 suitable for use in multiplexing multiple high speed
signals onto a shared transmission line. The LMH6720 is
also ideal for portable applications where current draw can
be reduced with the shutdown function.
Features
n 400MHz (AV = +2V/V, VOUT = 500mVPP) −3dB BW
n 250MHz (AV = +2V/V, VOUT = 2VPP) -3dB BW
n 0.1dB gain flatness to 120MHz
n Low power: 5.6mA
n TTL compatible shutdown pin (LMH6720)
n Very low diff. gain, phase: 0.01%, 0.01˚ (LMH6714)
n −58 HD2/ −70 HD3 at 20MHz
n Fast slew rate: 1800V/µs
n Low shutdown current: 500uA (LMH6720)
n 11ns turn on time (LMH6720)
n 7ns shutdown time (LMH6720)
n Unity gain stable
n Improved replacement for CLC400,401,402,404,406 and
446 (LMH6714)
n Improved replacement for CLC405 (LMH6720)
n Improved replacement for CLC415 (LMH6722)
Applications
n HDTV, NTSC & PAL video systems
n Video switching and distribution
n Wideband active filters
n Cable drivers
n High speed multiplexer (LMH6720)
n Programmable gain amplifier (LMH6720)
Non-Inverting Small Signal Frequency Response
Differential Gain and Phase vs. Number of Video
Loads (LMH6714)
20056506
© 2003 National Semiconductor Corporation DS200565
20056528
www.national.com
1 page  
Typical Performance Characteristics (AV = 2, RF = 300Ω, RL = 100Ω Unless Specified).
Non-Inverting Small Signal Frequency Response
Non-Inverting Large Signal Frequency Response
20056506
Inverting Frequency Response
20056507
Non-Inverting Frequency Response vs. VO
20056503
Inverting Frequency Response vs. VO
20056508
Harmonic Distortion vs. Frequency
20056509
5
20056504
www.national.com
5 Page 
Application Section (Continued)
WIDE BAND DIGITAL PROGRAMMABLE GAIN AMPLIFIER (LMH6720 ONLY)
FIGURE 6. Wideband Digitally Controlled Programmable Gain Amplifier
Channel Switching
20056519
20056520
FIGURE 7. PGA Output
As shown in Figure 6 and Figure 7 the LMH6720 can be
used to construct a digitally controlled programmable gain
amplifier. Each amplifier is configured to provide a digitally
selectable gain. To provide for accurate gain settings, 1% or
better tolerance is recommended on the feedback and gain
resistors. The gain provided by each digital code is arbitrary
through selection of the feedback and gain resistor values.
AMPLITUDE EQUALIZATION
Sending signals over coaxial cable greater than 50 meters in
length will attenuate high frequency signal components
much more than lower frequency components. An equalizer
can be made to pre emphasize the higher frequency com-
ponents so that the final signal has less distortion. This
process can be done at either end of the cable. The circuit in
Figure 8 shows a receiver with some additional components
in the feedback loop to equalize the incoming signal. The RC
networks peak the signal at higher frequencies. This peaking
is a piecewise linear approximation of the inverse of the
frequency response of the coaxial cable. Figure 9 shows the
effect of this equalization on a digital signal that has passed
through 150 meters of coaxial cable. Figure 10 shows a
Bode plot of the frequency response of the circuit in Figure 8
along with equations needed to design the pole and zero
frequencies. Figure 11 shows a network analyzer plot of an
LMH6714/6720/6722 with the following component values:
RG = 309Ω
R1 = 450Ω
C1 = 470pF
R2 = 91Ω
C2 = 68pF
11 www.national.com
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet LMH672.PDF ] | |
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