LMH6720MA Datasheet, PDF (14/29 Pages) Texas Instruments – LMH6714/ LMH6720/ LMH6722/ LMH6722Q Wideband Video Op Amp; Single, Single with Shutdown and Quad

LMH6714, LMH6720
LMH6722, LMH6722-Q1
SNOSA39G – NOVEMBER 2002 – REVISED APRIL 2013
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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 components so that the final signal has less distortion. This process can be done at either end
of the cable. The circuit in Figure 38 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 39 shows
the effect of this equalization on a digital signal that has passed through 150 meters of coaxial cable. Figure 40
shows a Bode plot of the frequency response of the circuit in Figure 38 along with equations needed to design
the pole and zero frequencies. Figure 41 shows a network analyzer plot of an LMH6714/LMH6720/LMH6722 with
the following component values:
R_G = 309Ω
R1 = 450Ω
C1 = 470pF
R2 = 91Ω
C2 = 68pF
Figure 38. Equalizer Circuit Schematic
Figure 39. Digital Signal without and with Equalization
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