EL4452C

Wideband Variable-Gain Amplifier with Gain of 10

Applications Information

Contd

In this circuit the EL4450 not only calculates the

square of the input but also provides the offset

integrator function The product of the two mul-

are

passed

to

the

output

amplifier

which

‘‘integrator’’ gain does not pass through zero at

high frequencies but has a zero at 1(2

k

X) This zero is cancelled by the pole caused by

exchanged for a positive reference by connecting

it to the ground return of the 1 k

X resistor at the

FB terminal and grounding REF

As a general consideration the input signal ap-

plied to an EL4452 should be kept below about

250 mV peak for good linearity If the AGC were

designed to produce a 1V peak output the input

range would be 100 mV – 250 mV peak when the

EL4452 has a feedback network that establishes a

maximum gain of 10 This is an input range of

only 251 for precise output regulation Raising

the maximum gain to 25 allows a 40 mV – 250 mV

input range with the output still regulated better

than 61 Unfortunately the bandwidth will be

reduced Bandwidth can be maintained by adding

a high frequency op-amp cascaded with the out-

put to make up gain beyond the 10 of the

EL4452 current feedback devices being the most

flexible The op-amp’s input should be capacitor

coupled to prevent gained-up offsets from confus-

ing the level detector during AGC control line

variations

General Disclaimer

Specifications contained in this data sheet are in effect as of the publication date shown Elantec Inc reserves the right to make changes

in the circuitry or specifications contained herein at any time without notice Elantec Inc assumes no responsibility for the use of any

circuits described herein and makes no representations that they are free from patent infringement

Elantec Inc

1996 Tarob Court

Milpitas CA 95035

Telephone (408) 945-1323

(800) 333-6314

Fax (408) 945-9305

European Office 44-71-482-4596

WARNING

Life Support Policy

Elantec Inc products are not authorized for and should not be

used within Life Support Systems without the specific written

consent of Elantec Inc Life Support systems are equipment in-

tended to support or sustain life and whose failure to perform

when properly used in accordance with instructions provided can

be reasonably expected to result in significant personal injury or

death Users contemplating application of Elantec Inc products

in Life Support Systems are requested to contact Elantec Inc

factory headquarters to establish suitable terms

conditions for

these applications Elantec Inc’s warranty is limited to replace-

ment of defective components and does not cover injury to per-

sons or property or other consequential damages

Printed in USA

12