OP282/OP482 Data Sheet
Rev. I | Page 12 of 16
APPLICATIONS INFORMATION
The OP282 and OP482 are dual and quad JFET op amps that
are optimized for high speed at low power. This combination
makes these amplifiers excellent choices for battery-powered or
low power applications that require above average performance.
Applications benefiting from this performance combination
include telecommunications, geophysical exploration, portable
medical equipment, and navigational instrumentation.
HIGH-SIDE SIGNAL CONDITIONING
Many applications require the sensing of signals near the positive
rail. OP282 and OP482 were tested and are guaranteed over a
common-mode range (−11 V ≤ V
CM
≤ +15 V) that includes the
positive supply.
One application where such sensing is commonly used is in the
sensing of power supply currents. Therefore, the OP282/OP482
can be used in current sensing applications, such as the partial
circuit shown in Figure 45. In this circuit, the voltage drop across
a low value resistor, such as the 0.1 Ω shown here, is amplified
and compared to 7.5 V. The output can then be used for current
limiting.
15V
100k
Ω
500k
Ω
0.1
Ω
500k
Ω
100k
Ω
R
L
1/2
OP282
00301-046
Figure 45. High-Side Signal Conditioning
PHASE INVERSION
Most JFET input amplifiers invert the phase of the input signal
if either input exceeds the input common-mode range. For the
OP282/OP482, a negative signal in excess of 11 V causes phase
inversion. This is caused by saturation of the input stage, leading
to the forward-biasing of a gate-drain diode. Phase reversal in
the OP282/OP482 can be prevented by using Schottky diodes to
clamp the input terminals to each other and to the supplies. In
the simple buffer circuit shown in Figure 46, D1 protects the op
amp against phase reversal. R1, D2, and D3 limit the input
current when the input exceeds the supply rail. The resistor
should be selected to limit the amount of input current below
the absolute maximum rating.
00301-042
D1
IN5711
V+
OP282/
OP482
V+
V
OUT
V
IN
V–
V–
D2
IN5711
R1
10kΩ
D3
IN5711
Figure 46. Phase Reversal Solution Circuit
00301-044
TIME (200µs/DIV)
VOLTAGE (5V/DIV)
2
V
S
= ±15V
V
IN
V
OUT
Figure 47. No Phase Reversal
ACTIVE FILTERS
The wide bandwidth and high slew rates of the OP282/OP482
make either one an excellent choice for many filter applications.
There are many active filter configurations, but the four most
popular configurations are Butterworth, elliptic, Bessel, and
Chebyshev. Each type has a response that is optimized for a
given characteristic, as shown in Table 4.
Table 4. Active Filter Configurations
Type Selectivity Overshoot Phase Amplitude (Pass Band) Amplitude (Stop Band)
Chebyshev Good Moderate Nonlinear Equal ripple
Elliptic Best Poor Equal ripple Equal ripple
Bessel (Thompson) Poor Best Linear
