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EL2082CN 查看數據表(PDF) - Elantec -> Intersil

零件编号
产品描述 (功能)
生产厂家
EL2082CN
Elantec
Elantec -> Intersil Elantec
EL2082CN Datasheet PDF : 16 Pages
First Prev 11 12 13 14 15 16
EL2082C
Current-Mode Multiplier
Applications Information Contd
The circuit sums two inputs A and B such that the sum of their respective path gains is unity as
controlled by the potentiometer When the potentiometer’s wiper is fully down the slightly negative
voltage at the Vg of the B-side EL2082 cuts off the B signal to better than 70 dB attenuation at
3 58 MHz The A-side EL2082 is at unity gain so the only (error) signal presented to the op-amp’s -in-
put is the same (error) signal at the IIN of the A-side EL2082 The circuit thus outputs -AIN Since the
error signal required by the op-amp is very small even at video frequencies the current through the A-
side EL2082 is small and distortion is minimized
At 50% potentiometer setting equal error output signals flow from the EL2082’s since the op-amp still
requires little net -input current The EL2082’s essentially buck each other to establish an output and
50% gain occurs for both the A and B inputs The EL2082’s now contribute distortion but less than in
previous connections The op-amp sees a constant 1k feedback resistor regardless of potentiometer
setting so frequency response is stable for all gain settings
A single-input gain control is implemented by simply grounding BIN
Distortion can be improved by increasing the input resistors to lower signal currents This will lower
the overall gain accordingly but will not affect bandwidth which is dependent upon the feedback
resistors Reducing the signal input amplitude is an analagous tactic but the noise floor will effectively
rise
Another strategy to reduce distortion in video systems is to use DC restoration circuitry such as the
EL2090 ahead of the fader inputs to reduce the range of signals to be dealt with the b0 7V to a0 7V
possible range of inputs (due to capacitor coupling) would be changed to a stabilized b0 35V to a0 35V
span
The EL2020 EL2030 and EL2120 (at reduced bandwidth since it is compensated for 300X feedback
resistors) all give the same video performance at NTSC operation
Variable Filters
This circuit is the familiar state-variable configuration similar to the bi-quad
Voltage Tuneable Bi-Quad Filter
 J Vg
1
F0 e 1V 2q (R a 95X)C
13
2082 – 23

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