AN-732

APPLICATION NOTE

One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106 • Tel: 781/329-4700 • Fax: 781/326-8703 • www.analog.com

INTRODUCTION

The EVAL-PRAOPAMP-1R is an evaluation board which

accommodates single op amps in SOIC packages. It is

meant to provide the user with multiple choices and

extensive flexibility for different applications circuits

and configurations. This board is not intended to be

used with high frequency components or high speed

amplifiers. However, it provides the user with many

combinations for various circuit types including active

filters, differential amplifiers, and external frequency

compensation circuits. A few examples of application

circuits are given in this application note.

RELATIVE FREQUENCY

f

–20

0

40

20

60

10f

100f

1000f

10000f

R7/R2 = 100

R7

R2

R6

C7

Figure 1. Simple Low-Pass Filter

Universal Precision Op Amp Evaluation Board in SOIC Package

by Giampaolo Marino, Soufiane Bendaoud, and Steve Ranta

LOW-PASS FILTER

Figure 1 is a typical representation of a first-order low-

pass filter. This circuit has a 6 dB per octave roll- off

this frequency is defined as the magnitude of R7 to R2.

The circuit might be considered as an ac integrator for

response is that of a single RC, rather than an integral.

R7

C7); –3 dB frequency

R2

C7); unity gain frequency

Acl = – (R7/R2); close loop gain

R6 should be chosen equal to the parallel combination

between R7 and R2 in order to minimize errors due to

bias currents.

R7

R2

R4

R6

Figure 2. Difference Amplifier

DIFFERENCE AMPLIFIER AND PERFORMANCE

OPTIMIZATION

Figure 2 shows an op amp configured as a difference

amplifier. The difference amplifier is the complement

of the summing amplifier, and allows the subtraction

of two voltages or the cancellation of a signal common

to both inputs. The circuit shown in Figure 2 is useful

as a computational amplifier in making a differential

to single-ended conversion or in rejecting a common-

two separate components:

short-circuited to ground.)

short-circuited to ground.)

REV. A