8

FN7344.4

May 10, 2007

Simplified Schematic

Description of Operation and Application

Information

Product Description

The EL5177 is a wide bandwidth, low power and

single/differential ended to differential output amplifier. It can

be used as single/differential ended to differential converter.

The EL5177 is internally compensated for closed loop gain

of +1 of greater. Connected in gain of 1 and driving a 1k

Ω

differential load, the EL5177 has a -3dB bandwidth of

550MHz. Driving a 200

Ω differential load at gain of 2, the

bandwidth is about 130MHz. The EL5177 is available with a

power down feature to reduce the power while the amplifier

is disabled.

Input, Output, and Supply Voltage Range

The EL5177 has been designed to operate with a single

supply voltage of 5V to 10V or a split supplies with its total

voltage from 5V to 10V. The amplifiers have an input

common mode voltage range from -4.3V to 3.4V for ±5V

supply. The differential mode input range (DMIR) between

the two inputs is from -2.3V to +2.3V. The input voltage

range at the REF pin is from -3.3V to 3.7V. If the input

common mode or differential mode signal is outside the

above-specified ranges, it will cause the output signal

distorted.

The output of the EL5177 can swing from -3.8V to +3.8V at

1k

Ω differential load at ±5V supply. As the load resistance

becomes lower, the output swing is reduced.

Differential and Common Mode Gain Settings

The voltage applied at REF pin can set the output common

mode voltage and the gain is one. The differential gain is set

The gain setting for EL5177 is:

Where:

FIGURE 23.

Choice of Feedback Resistor and Gain Bandwidth

Product

For applications that require a gain of +1, no feedback

resistor is required. Just short the OUT+ pin to FBP pin and

OUT- pin to FBN pin. For gains greater than +1, the

feedback resistor forms a pole with the parasitic capacitance

at the inverting input. As this pole becomes smaller, the

amplifier's phase margin is reduced. This causes ringing in

the time domain and peaking in the frequency domain.

REF

OUT+

OUT-

FBN

FBP

IN-

IN+

V

ODM

V

IN

(

+V

1

R

F1

R

F2

+

R

G

----------------------------

+

⎝⎠

⎜⎟

⎛⎞

×

–

=

V

ODM

V

IN

(

+V

1

2R

F

R

G

-----------

+

⎝⎠

⎜⎟

⎛⎞

×

–

=

V

OCM

V

REF

=

FBP

REF

FBN

EL5177