EL2090CM 데이터 시트보기 (PDF) - Elantec -> Intersil
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EL2090CM Datasheet PDF : 12 Pages
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EL2090C
100 MHz DC-Restored Video Amplifier
Applications Information Contd
a saturation voltage we prevent this node from
approaching the positive rail The maximum
voltage is set by the resistive voltage divider (be-
tween Va and GND) R1 and R2 plus a diode
This value can be adjusted if the maximum size
of the input signal is known The diode used is an
off-the-shelf 1N914 or 1N916
As is true of all 100 MHz amplifiers good by-
passing of the supplies to ground is mandatory
1 mF tantalums are sufficient and 0 01 mF leaded
chip capacitors in parallel with medium value
electrolytics are also good Leads longer than
can induce a characteristic 150 MHz resonance
and ringing
The VINb of the video amplifier should have the
absolute minimum of parasitic capacitance Stray
capacitance of more than 3 pF will cause peaking
and compromise the gain flatness The band-
width of the amplifier is fundamentally set by
the value of Rf As demonstrated by the frequen-
cy response versus gain graph the peaking and
bandwidth is a weak function of gain The
EL2090 was designed for Rf e 300X giving opti-
mum gain flatness at Av e a2 Unity-gain re-
sponse is flattest for Rf e 360X gains of a5 can
use Rf e 270X In situations where the peaking
is accentuated by load capacitance or binput ca-
pacitance the value of Rf will have to be in-
creased and some bandwidth will be sacrificed
The VINa of the video amplifier should not look
into an inductive source impedance If the source
is physically remote and a terminated input line
is not provided it may be necessary to connect
an input ‘‘snubber’’ to ground A snubber is a re-
sistor in series with a capacitor which de-Q’s the
input resonance Typical values are 100X and
30 pF
The output of the video amplifier is sensitive to
capacitive loads greater than 25 pF and a snub-
ber to ground or a resistor in series with the out-
put is useful to isolate reactive loads
9
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