EL2142 Просмотр технического описания (PDF) - Renesas Electronics

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EL2142

Differential Line Receiver

Renesas Electronics 

EL2142

Applications Information

Gain Equation

VOUT = ((R2+R1)/R1) x (VIN-VINB+VREF) when R1 tied to

GND

VOUT = ((R2+R1)/R1) x (VIN-VINB) when R1 tied to VREF

Choice of Feedback Resistor

For a gain of one, VOUT may be shorted back to VFB, but

100-200 improves the bandwidth. For gains greater than

Typical Applications Circuits

one, there is little to be gained from choosing resistor R1

value below 200, for it would only result in increased power

dissipation and potential signal distortion. Above 200, the

bandwidth response will develop some peaking (for a gain of

one), but substantially higher R1 values may be used for

higher voltage gains, such as up to 1k at a gain of four

before peaking will develop.

Capacitance Considerations

As with many high bandwidth amplifiers, the EL2142 prefers

not to drive highly capacitive loads. It is best if the

capacitance on VOUT is kept below 10pF if the user does not

want gain peaking to develop. The VFB node forms a

potential pole in the feedback loop, so capacitance should

be minimized on this node for maximum bandwidth.

The amount of capacitance tolerated on any of these nodes

in an actual application will also be dependent on the gain

setting and the resistor values in the feedback network.

100

50

VFB

VIN

EL2142

VINB

50

VREF

VOUT

FIGURE 1. TYPICAL TWISTED PAIR APPLICATION

FIGURE 2. COAXIAL CABLE DRIVER PAIR APPLICATION

FN7049 Rev 1.00

February 11, 2005

Page 4 of 6

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