OP249
Data Sheet
Rev. H | Page 14 of 20
10
0%
100
90
50mV
1s
00296-
042
Figure 42. Small-Signal Transient Response,
AV = 1, ZL = 2 k||100 pF, No Compensation, VS = ±15 V
As with most JFET input amplifiers, the output of th
e OP249can undergo phase inversion if either input exceeds the specified
input voltage range. Phase inversion does not damage the
amplifier, nor does it cause an internal latch-up condition.
Supply decoupling should be used to overcome inductance and
resistance associated with supply lines to the amplifier. A 0.1 F
and a 10 F capacitor should be placed between each supply pin
and ground.
OPEN-LOOP GAIN LINEARITY
1 kV/mV minimum and constant gain linearity, which enhances its
dc precision and provides superb accuracy in high closed-loop
gain application
s. Figure 43 illustrates the typical open-loop
gain linearity—high gain accuracy is assured, even when
driving a 600 Ω load.
OFFSET VOLTAGE ADJUSTMENT
The inherent low offset voltage of th
e OP249 makes offset
adjustments unnecessary in most applications. However, where
a lower offset error is required, balancing can be performed
HORIZONTAL 5V/DIV
OUTPUT CHARGE
VERTICAL 50V/DIV
INPUT VARIATION
00296-
043
Figure 43. Open-Loop Gain Linearity; Variation in Open-Loop Gain Results in
Errors in High Closed-Loop Gain Circuits; RL = 600 , VS = ±15 V
+V
R3
R4
R2
R1
VOS ADJUST RANGE = ±V
VOUT
VIN
–V
1/2
OP249
R2
31
R5
50k
R1
200k
00296-
044
Figure 44. Offset Adjustment for Inverting Amplifier Configuration
+V
R5
VOS ADJUST RANGE = ±V
R2
R1
1 +
R5
R4
IF R2 << R4
R5
R4 + R2
R4
VOUT
–V
VIN
R3
50k
R2
33
R1
200k
1/2
OP249
GAIN =
= 1 +
VOUT
VIN
=
00296-
045
Figure 45. Offset Adjustment for Noninverting Amplifier Configuration
In
Figure 44, the offset adjustment is made by supplying a small
voltage at the noninverting input of the amplifier. Resistors R1
and R2 attenuate the potentiometer voltage, providing a ±2.5 mV
(with VS = ±15 V) adjustment range, referred to the input.
Figure 45 shows the offset adjustment for the noninverting
amplifier configuration, also providing a ±2.5 mV adjustment
range. As shown in the equations i
n Figure 45, if R4 is not much
greater than R2, a resulting closed-loop gain error must be
accounted for.
SETTLING TIME
The settling time is the time between when the input signal begins
to change and when the output permanently enters a prescribed
error band. The error bands on the output are 5 mV and 0.5 mV,
respectively, for 0.1% and 0.01% accuracy.
870 ns. Moreover, problems in settling response, such as thermal
tails and long-term ringing, are nonexistent.
10
0%
100
90
500ns
10mV
870ns
00296-
046
Figure 46. Settling Characteristics of th
e OP249 to 0.01%