9

Simplified Schematic Diagram

Description of Operation and Application

Information

Product Description

The EL8300 is wide bandwidth, single supply, low power and

rail-to-rail output voltage feedback operational amplifier. The

amplifiers are internally compensated for closed loop gain of

+1 of greater. Connected in voltage follower mode and

driving a 1k

Ω load, the EL8300 has a -3dB bandwidth of

200MHz. Driving a 150

Ω load, the bandwidth is about

130MHz while maintaining a 200V/us slew rate. The EL8300

is available with a power down pin for each channel to

reduce power to 30µA typically while the amplifier is

disabled.

Input, Output and Supply Voltage Range

The EL8300 has been designed to operate with a single

supply voltage from 3V to 5.0V. Split supplies can also be

used as long as their total voltage is within 3V to 5.0V. The

amplifiers have an input common mode voltage range from

above specified range, it will cause the output signal to be

distorted.

The output of the EL8300 can swing rail to rail. As the load

resistance becomes lower, the ability to drive close to each

rail is reduced. For the load resistor 1k

Ω, the output swing is

about 4.9V at a 5V supply. For the load resistor 150

Ω, the

output swing is about 4.6V.

Choice of Feedback Resistor and Gain Bandwidth

Product

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

resistor is required. Just short the output pin to the inverting

input 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

some maximum value that should not be exceeded for

can help to reduce the ringing and peaking at the expense of

reducing the bandwidth.

As far as the output stage of the amplifier is concerned, the

combination gets smaller, the bandwidth falls off.

is optimum. For the gains other than +1, optimum response

The EL8300 has a gain bandwidth product of 100MHz. For

gains

≥5, its bandwidth can be predicted by the following

equation:

Video Performance

For good video performance, an amplifier is required to

maintain the same output impedance and the same

frequency response as DC levels are changed at the output.

This is especially difficult when driving a standard video load

of 150

Ω, because the change in output current with DC level.

Special circuitry has been incorporated in the EL8300 to

reduce the variation of the output impedance with the current

output. This results in dG and dP specifications of 0.03%

and 0.05

°, while driving 150Ω at a gain of 2. Driving high

impedance loads would give a similar or better dG and dP

performance.

IN+

IN-

OUT

DIFFERENTIAL TO

DRIVE

GENERATOR

SINGLE ENDED

Gain

BW

×

100MHz

=

EL8300