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EL2073C

200MHz Unity-Gain Stable Operational Amplifier

Applications Information

Product Description

The EL2073C is a wideband monolithic operational

amplifier built on a high-speed complementary bipolar

process. The EL2073C uses a classical voltage-feedback

topology which allows it to be used in a variety of appli-

cations where current-feedback amplifiers are not

appropriate because of restrictions placed upon the feed-

back element used with the amplifier. The conventional

topology of the EL2073C allows, for example, a capaci-

tor 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

EL2073C is an excellent choice for applications such as

log amplifiers.

The EL2073C also has excellent DC specifications:

These specifications allow the EL2073C to be used in

DC-sensitive applications such as difference amplifiers.

Furthermore, the current noise of the EL2073C is only

3.2 pA/Hz, making it an excellent choice for high-sensi-

tivity transimpedance amplifier configurations.

Gain-Bandwidth Product

The EL2073C has a gain-bandwidth product of

200MHz. 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

bandwidths. For example, the EL2073C has a -3dB

bandwidth of 400MHz at a gain of +1, dropping to

200MHz at a gain of +2. It is important to note that the

EL2073C 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 EL2073C in a gain of +1 only exhibits 1dB

of peaking with a 100

Ω load.

Video Performance

An industry-standard method of measuring the video

distortion of a component such as the EL2073C 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, 4.43MHz for PAL, or 30MHz for HDTV. 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 per-

cent. 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 EL2073C has been designed to be among the best

video amplifiers in the marketplace today. It has been

thoroughly characterized for video performance in the

topology described above, and the results have been

included as minimum dG and dP specifications and as

typical performance curves. In a gain of +2, driving

150

Ω, with standard video test levels at the input, the

EL2073C exhibits dG and dP of only 0.01% and 0.015°

at NTSC and PAL. Because dG and dP vary with differ-

ent DC offsets, the superior video performance of the

EL2073C 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.

The excellent output drive capability of the EL2073C

allows it to drive up to 4 back-terminated loads with

excellent video performance. With 4 150

Ω loads, dG

and dP are only 0.15% and 0.08° at NTSC and PAL. For

more information, refer to the curves for Video Perfor-

mance vs Number of 150

Ω Loads.

Output Drive Capability

The EL2073C has been optimized to drive 50

Ω and 75Ω

output drive capability makes the EL2073C an ideal

choice for RF, IF and video applications. Furthermore,