EL4094 データシートの表示（PDF） - Intersil
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EL4094 Datasheet PDF : 12 Pages
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EL4094
±5V to ±12V levels, especially if extra dissipation occurs
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 typical situation would be to scale a
variable video input by +6dB to -6dB to obtain a standard
amplitude. The EL4094 cannot provide more than 0dB gain,
but it can span the range of 0dB to -12dB with another
amplifier gaining the output up by 6dB. 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 linearity degrades at low gains. By
connecting the signal to the A input of the EL4094 and the
signal attenuated by 12dB to the B input, the gain control
offers the highest linearity possible at 0dB and -12dB
extremes, and good performance between. 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
voltage. Here is the curve of differential gain and phase
distortion for varying inputs, with the output set to standard
video level:
FIGURE 2. DIFFERENTIAL GAIN AND PHASE OF
LINEARIZED LEVEL CONTROL
The differential gain error is kept to 0.3% and the differential
phase to 0.15° or better over the entire input range.
The EL4094 as an Adjustable Filter
Equalizers are used to adjust the delay or frequency
response of systems. A typical use is to compensate for the
high-frequency loss of a cable system ahead of the cable so
as to create a flat response at the far end. A generalized
scheme with the EL4094 is shown below.
FIGURE 3. +6dB to -6dB LINEARIZED LEVEL CONTROL
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