EL4095CS INTERSIL [Intersil Corporation], EL4095CS Datasheet - Page 11

• Manufacturer Part Number: EL4095CS
• Description: Video Gain Control/Fader/Multiplexer
• Manufacturer: INTERSIL [Intersil Corporation]

Stray capacitance at each -V
minimized, especially in a positive-gain mode, or peaking will
occur. Similarly, the load capacitance should be minimized. If
more than 25pF of load capacitance must be driven, a load
resistor from 100Ω to 400Ω can be added in parallel with the
output to reduce peaking, but some bandwidth degradation
may occur. A “snubber” load can alternatively be used. This
is a resistor in series with a capacitor to ground, 150Ω and
100pF being typical values. The advantage of a snubber is
that it does not draw DC load current. A small series resistor,
low tens of ohms, can also be used to isolate reactive loads.
Distortion
The signal voltage range of the +V
of either supply rail.
One must also consider the range of error currents that will
be handled by the -V
the output of a buffer which replicates the voltage at +V
error currents will flow into the -V
channel has 100% gain assigned to it, only a small error
current flows into its negative input; when low gain is
assigned to the channel the output does not respond to the
channel’s signal and large error currents flow.
IN
terminals. Since the -V
IN
11
terminal should absolutely be
IN
IN
terminal. When an input
FIGURE 1. EL4095 IN INVERTING CONNECTION
terminals is within 3.5V
IN
of a CFA is
IN
,
EL4095
Here are a few idealized examples, based on a gain of +1 for
channels A and B and R
Thus, either -V
of input signal and 1kΩ feedback resistors. The maximum
error current is 3mA for the EL4095, but 2mA is more
realistic. The major contributor of distortion is the magnitude
of error currents, even more important than loading effects.
The performance curves show distortion versus input
amplitude for different gains.
If maximum bandwidth is not required, distortion can be
reduced greatly (and signal voltage range enlarged) by
increasing the value of R
resistor.
100%
Gain
75%
50%
25%
0%
V
1V
1V
1V
1V
1V
INA
IN
can receive up to 1mA error current for 1V
V
INB
F
0
0
0
0
0
F
= 1kΩ for different gain settings:
and any associated gain-setting
I (-V
-250µA
-500µA
-750µA
-1mA
0
INA
)
I (-V
750µA
500µA
250µA
1mA
0
INB
)
0.75V
0.25V
V
0.5V
OUT
1V
0V