OP249

Rev. F | Page 13 of 20

APPLICATIONS INFORMATION

+IN

V+

V–

–IN

Figure 39. Simplified Schematic (1/2 OP249)

+3V

+18V

+3V

5kΩ

5kΩ

1/2

OP249

1/2

OP249

2

1

3

6

5

4

8

7

–18V

Figure 40. Burn-In Circuit

The OP249 represents a reliable JFET amplifier design,

featuring an excellent combination of dc precision and high

speed. A rugged output stage provides the ability to drive a

600 Ω load and still maintain a clean ac response. The OP249

features a large signal response that is more linear and symmetric

than previously available JFET input amplifiers. Figure 41

compares the large signal response of the OP249 to other

industry-standard dual JFET amplifiers.

Typically, the slewing performance of the JFET amplifier is

specified as a number of V/μs. There is no discussion on the

quality, that is, linearity and symmetry of the slewing response.

10

0%

100

90

A) OP249

10

0%

100

90

B) LT1057

10

0%

100

90

C) AD712

1µs

5V

1µs

5V

1µs

5V

Figure 41. Large-Signal Transient Response,

The OP249 was carefully designed to provide symmetrically

matched slew characteristics in both the negative and positive

directions, even when driving a large output load.

The slewing limitation of the amplifier determines the

maximum frequency at which a sinusoidal output can be

obtained without significant distortion. However, it is important

to note that the nonsymmetric slewing typical of previously

available JFET amplifiers adds a higher series of harmonic

energy content to the resulting response—and an additional

dc output component. Examples of potential problems of

nonsymmetric slewing behavior can be in audio amplifier

applications, where a natural low distortion sound quality is

desired and in servo or signal processing systems where a net

dc offset cannot be tolerated. The linear and symmetric slewing

feature of the OP249 makes it an ideal choice for applications

that exceed the full power bandwidth range of the amplifier.