AD8682ARZ Analog Devices Inc, AD8682ARZ Datasheet - Page 10

• Manufacturer Part Number: AD8682ARZ
• Description: IC OPAMP JFET 3.5MHZ DUAL 8SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD8682ARZ

• Slew Rate: 9 V/µs
• Amplifier Type: J-FET
• Number Of Circuits: 2
• Gain Bandwidth Product: 3.5MHz
• Current - Input Bias: 6pA
• Voltage - Input Offset: 350µV
• Current - Supply: 210µA
• Current - Output / Channel: 12mA
• Voltage - Supply, Single/dual (±): 9 V ~ 36 V, ±4.5 V ~ 18 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Op Amp Type: General Purpose
• No. Of Amplifiers: 2
• Bandwidth: 3.5MHz
• Supply Voltage Range: ± 4.5V To ± 18V
• Amplifier Case Style: SOIC
• No. Of Pins: 8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Output Type: -
• -3db Bandwidth: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

AD8682/AD8684
APPLICATIONS INFORMATION
The AD8682 and AD8684 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
There are many applications requiring the sensing of signals near
the positive rail. The AD8682 and the AD8684 were tested and
are guaranteed over a common-mode range (−11 V ≤ V
+15 V) that includes the positive supply.
The AD8682/AD8684 are commonly used in the sensing of
power supply currents and in current sensing applications, such
as the partial circuit shown in Figure 32. 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.
Table 4.
Type
Butterworth
Chebyshev
Elliptical
Bessel (Thompson)
15V
100kΩ
500kΩ
Figure 32. High-Side Signal Conditioning
0.1Ω
100kΩ
Best
Selectivity
Moderate
Good
Poor
AD8682
1/2
500kΩ
Overshoot
Good
Moderate
Poor
Best
R
L
CM
≤
Rev. A | Page 10 of 16
Phase
Nonlinear
Linear
PHASE INVERSION
Most JFET input amplifiers invert the phase of the input signal
if either input exceeds the input common-mode range. For the
AD8682/AD8684, negative signals in excess of approximately
14 V cause phase inversion. This is caused by saturation of the
input stage leading to the forward-biasing of a drain-gate diode.
A simple fix for this in noninverting applications is to place
a resistor in series with the noninverting input. This limits the
amount of current through the forward-biased diode and prevents
shutting down of the output stage. For the AD8682/AD8684,
a value of 200 kΩ has been found to work; however, it adds
a significant amount of noise.
ACTIVE FILTERS
The wide bandwidth and high slew rates of the AD8682/AD8684
make either one an excellent choice for many filter applications.
There are many active filter configurations, but the four most
popular configurations are: Butterworth, elliptical, Bessel, and
Chebyshev. Each type has a response that is optimized for a
given characteristic, as shown in Table 4.
Amplitude (Pass Band)
Maximum flat
Equal ripple
Equal ripple
–10
–15
15
10
–5
–15
5
0
–10
Figure 33. AD8682 Phase Reversal
–5
V
0
IN
Amplitude (Stop Band)
Equal ripple
5
10
15