el4094c ETC-unknow, el4094c Datasheet - Page 9

• Manufacturer Part Number: el4094c
• Description: Video Gain Control/fader
• Manufacturer: ETC-unknow

Applications Information
sistor in series with a capacitor 150
being typical values The advantage of a snubber
is that it does not draw DC load current
Unterminated coaxial line loads can also cause
resonances and they should be terminated either
at the far end or a series back-match resistor in-
stalled between the EL4094 and the cable
The output stage can deliver up to 140 mA into a
short-circuit load but it is only rated for a con-
tinuous 35 mA More continuous current can
cause reliability problems with the on-chip metal
interconnect Video levels and loads cause no
problems at all
Noise
The EL4094 has a very simple noise characteris-
tic the output noise is constant (40 nV
wideband) for all gain settings The input-re-
ferred noise is then the output noise divided by
the gain For instance at a gain of 50% the input
noise is 40 nV
Bypassing
The EL4094 is fairly tolerant of power-supply
bypassing but best multiplier performance is ob-
tained with closely connected 0 1 F ceramic ca-
pacitors The leaded chip capacitors are good but
neither additional tantalums nor chip compo-
nents are necessary The signal inputs can oscil-
late locally when connected to long lines or un-
terminated cables
Power Dissipation
Peak die temperature must not exceed 150 C At
this temperature the epoxy begins to soften and
becomes unstable chemically and mechanically
This allows 75 C internal temperature rise for a
75 C ambient The EL4094 in the 8-pin PDIP
package has a thermal resistance of 87 W and
can thus dissipate 862 mW at a 75 C ambient
temperature The device draws 17 mA maximum
supply current only 510 mW at
and the circuit has no dissipation problems in
this package
The SO-8 surface-mount package has a 153 W
thermal resistance with the EL4094 and only
490 mW can be dissipated at 75 C ambient tem-
S
Hz 0 5 or 80 nV
g
S
15V supplies
Hz
and 100 pF
Contd
S
Hz
9
perature The EL4094 thus cannot be operated
with
package the supplies should be reduced to
to
curs when driving a load
The EL4094 as a Level Adjust
A common use for gain controls is as an input
signal leveller a circuit that scales too-large or
too-small signals to a standard amplitude A typi-
cal situation would be to scale a variable video
input by
amplitude The EL4094 cannot provide more
than 0 dB gain but it can span the range of 0 dB
to
output up by 6 dB The simplest way to obtain
the range is to simply ground the B input and
vary the gain of the signal applied to the A input
The disadvantage of this approach is that lineari-
ty degrades at low gains By connecting the sig-
nal to the A input of the EL4094 and the signal
attenuated by 12 dB to the B input the gain con-
trol offers the highest linearity possible at 0 dB
and
tween The circuit is shown on the following
page
The EL4095 can be used to provide the required
gains without the extra amplifier In practice the
gain control is adjusted to set a standard video
level regardless of the input level The EL4583
sync-separator has a recovered amplitude output
that can be used to servo the gain control volt-
age Here is the curve of differential gain and
phase distortion for varying inputs with the out-
put set to standard video level
g
b
b
12V levels especially if extra dissipation oc-
g
12 dB with another amplifier gaining the
Video Gain Control Fader
12 dB extremes and good performance be-
15V supplies at 75 C in the surface-mount
Differential Gain and Phase of
a
6 dB to
Linearized Level Control
b
6 dB to obtain a standard
EL4094C
4094 – 14
g
5V