OP249_07 Datasheet, PDF (13/20 Pages) Analog Devices – Dual, Precision JFET High Speed Operational Amplifier

APPLICATIONS INFORMATION
V+
+IN
–IN
V_OUT
V–
Figure 39. Simplified Schematic (1/2 OP249)
2
1/2
OP249 ¹
+3V
3
5kΩ
+18V
6
8
1/2
OP249
7
+3V
5
4
5kΩ
–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.
OP249
100
90
10
0%
5V
100
90
1µs
A) OP249
10
0%
5V
100
90
1µs
B) LT1057
10
0%
5V
1µs
C) AD712
Figure 41. Large-Signal Transient Response,
AV = 1, VIN = 20 V p-p, ZL = 2 kΩ//200 pF, VS = ±15 V
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.
Rev. F | Page 13 of 20