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EL2044C

Low Power/Low Voltage 120MHz Unity-Gain Stable Operational Amplifier

Applications Information

Product Description

The EL2044C is a low-power wideband monolithic

operational amplifier built on Elantec's proprietary high-

speed complementary bipolar process. The EL2044C

uses a classical voltage-feedback topology which allows

it to be used in a variety of applications where current-

feedback amplifiers are not appropriate because of

restrictions placed upon the feedback element used with

the amplifier. The conventional topology of the

EL2044C allows, for example, a capacitor to be placed

in the feedback path, making it an excellent choice for

applications such as active filters, sample-and-holds, or

integrators. Similarly, because of the ability to use

diodes in the feedback network, the EL2044C is an

excellent choice for applications such as fast log

amplifiers.

Single-Supply Operation

The EL2044C has been designed to have a wide input

and output voltage range. This design also makes the

EL2044C an excellent choice for single-supply opera-

tion. Using a single positive supply, the lower input

and the lower output voltage range is within 300mV of

ground. Upper input voltage range reaches 4.2V, and

output voltage range reaches 3.8V with a 5V supply and

gle 5V supply. This wide output voltage range also

allows single-supply operation with a supply voltage as

high as 36V or as low as 2.5V. On a single 2.5V supply,

the EL2044C still has 1V of output swing.

Gain-Bandwidth Product and the -3dB

Bandwidth

The EL2044C has a gain-bandwidth product of 60MHz

while using only 5.2mA of supply current. For gains

greater than 4, its closed-loop -3dB bandwidth is

approximately equal to the gain-bandwidth product

divided by the noise gain of the circuit. For gains less

than 4, higher-order poles in the amplifier's transfer

function contribute to even higher closed loop band-

widths. For example, the EL2044C has a -3dB

bandwidth of 120MHz at a gain of +1, dropping to

60MHz at a gain of +2. It is important to note that the

EL2044C has been designed so that this “extra” band-

width in low-gain applications does not come at the

expense of stability. As seen in the typical performance

curves, the EL2044C in a gain of +1 only exhibits 1.0dB

of peaking with a 1000

Ω load.

Video Performance

An industry-standard method of measuring the video

distortion of a component such as the EL2044C is to

measure the amount of differential gain (dG) and differ-

ential phase (dP) that it introduces. To make these

the device with 0V DC offset (0 IRE) at either 3.58MHz

for NTSC or 4.43MHz for PAL. A second measurement

is then made at 0.714V DC offset (100 IRE). Differential

gain is a measure of the change in amplitude of the sine

wave, and is measured in percent. Differential phase is a

measure of the change in phase, and is measured in

degrees.

For signal transmission and distribution, a back-termi-

nated cable (75

Ω in series at the drive end, and 75Ω to

ground at the receiving end) is preferred since the

impedance match at both ends will absorb any reflec-

tions. However, when double termination is used, the

received signal is halved; therefore a gain of 2 configu-

ration is typically used to compensate for the

attenuation.

The EL2044C has been designed as an economical solu-

tion for applications requiring low video distortion. It

has been thoroughly characterized for video perfor-

mance in the topology described above, and the results

have been included as typical dG and dP specifications

and as typical performance curves. In a gain of +2, driv-

ing 150¾, with standard video test levels at the input, the

EL2044C exhibits dG and dP of only 0.04% and 0.15° at

NTSC and PAL. Because dG and dP can vary with dif-

ferent DC offsets, the video performance of the

EL2044C has been characterized over the entire DC off-

set range from -0.714V to +0.714V. For more

information, refer to the curves of dG and dP vs DC

Input Offset.