EL4095CS datasheet(13/19 Pages) INTERSIL

13 / 19 page

Here the A input channel is configured for a gain of +2 and

the B channel for a gain of +1 with its input attenuated by

1/2. The connection is virtuous because the distortions do

not increase monotonically with reducing gain as would the

simple single-input connection.

For video levels, however, these constants can give fairly

high differential gain error. The problem occurs for large

inputs. Assume that a “twice-size” video input occurs. The A-

side stage sees the full amplitude, but the gain would be set

to 100% B-input gain to yield an overall gain of 1/2 to

produce a standard video output. The -VIN of the A side is a

buffer output that reproduces the input signal, and drives

RGA and RFA. Into the two resistors 2.1mA of error current

flows for a typical 1.4V of input DC offset, creating distortion

in a A-side input stage. RGA and RFA could be increased

together in value to reduce the error current and distortions,

but increasing RFA would lower bandwidth. A solution would

be to simply attenuate the input signal magnitude and

restore the EL4095 output level to standard level with

another amplifier so:

FIGURE 3. LEVELING CIRCUIT WITH 0.5

≤ AV ≤ 2

EL4095

EL4095CS Datasheet(PDF) 13 Page - Intersil Corporation