AD8620ARZ Analog Devices Inc, AD8620ARZ Datasheet - Page 20

• Manufacturer Part Number: AD8620ARZ
• Description: IC OPAMP JFET 25MHZ DUAL 8SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD8620ARZ

• Slew Rate: 60 V/µs
• Design Resources: Using AD7328 in Appls with Single-Ended Industrial-Level Signals (CN0047)
• Amplifier Type: J-FET
• Number Of Circuits: 2
• Gain Bandwidth Product: 25MHz
• Current - Input Bias: 3pA
• Voltage - Input Offset: 85µV
• Current - Supply: 3mA
• Current - Output / Channel: 45mA
• Voltage - Supply, Single/dual (±): ±5 V ~ 13 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Op Amp Type: Precision
• No. Of Amplifiers: 2
• Bandwidth: 25MHz
• Supply Voltage Range: ± 5V To ± 13V
• 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

AD8610/AD8620
High Speed Instrumentation Amplifier
The 3-op-amp instrumentation amplifiers shown in Figure 68 can
provide a range of gains from unity up to 1000 or higher. The
instrumentation amplifier configuration features high common-
mode rejection, balanced differential inputs, and stable, accurately
defined gain. Low input bias currents and fast settling are achieved
with the JFET input AD8610/AD8620. Most instrumentation
amplifiers cannot match the high frequency performance of this
circuit. The circuit bandwidth is 25 MHz at a gain of 1, and close to
5 MHz at a gain of 10. Settling time for the entire circuit is 550 ns to
0.01% for a 10 V step (gain = 10). Note that the resistors around
the input pins need to be small enough in value so that the RC
time constant they form in combination with stray circuit capaci-
tance does not reduce circuit bandwidth.
High Speed Filters
The four most popular configurations are Butterworth, Elliptical,
Bessel (Thompson), and Chebyshev. Each type has a response
that is optimized for a given characteristic, as shown in Table 6.
Table 6. Filter Types
Type
Butterworth
Chebyshev
Elliptical
Bessel (Thompson)
+INB
+INA
RG
Figure 68. High Speed Instrumentation Amplifier
3
2
5
6
1/2 AD8620
1/2 AD8620
2kΩ
R4
2kΩ
U1
10pF
R8
U1
1kΩ
V+
V–
R2
8
4
C2
2kΩ
R7
10pF
1kΩ
R1
C5
1
7
C4
15pF
Sensitivity
Moderate
Good
Best
Poor
3
2
AD8610
U2
V+
V–
7
4
15pF
2kΩ
C3
R5
6
Overshoot
Good
Moderate
Poor
Best
R6
2kΩ
V
OUT
Rev. F | Page 20 of 24
In active filter applications using operational amplifiers, the dc
accuracy of the amplifier is critical to optimal filter performance.
The offset voltage and bias current of the amplifier contribute to
output error. Input offset voltage is passed by the filter and can
be amplified to produce excessive output offset. For low frequency
applications requiring large value input resistors, bias and offset
currents flowing through these resistors also generate an offset
voltage.
At higher frequencies, the dynamic response of the amplifier
must be carefully considered. In this case, slew rate, bandwidth,
and open-loop gain play a major role in amplifier selection.
The slew rate must be both fast and symmetrical to minimize
distortion. The bandwidth of the amplifier, in conjunction with the
gain of the filter, dictates the frequency response of the filter. The
use of high performance amplifiers, such as the AD8610/AD8620,
minimizes both dc and ac errors in all active filter applications.
Second-Order, Low-Pass Filter
Figure 69 shows the AD8610 configured as a second-order,
Butterworth, low-pass filter. With the values as shown, the
design corner was 1 MHz, and the bench measurement was
974 kHz. The wide bandwidth of the AD8610/AD8620 allows
corner frequencies into the megahertz range, but the input
capacitances should be taken into account by making C1 and
C2 smaller than the calculated values. The following equations
can be used for component selection:
where C1 and C2 are in farads.
R1 = R2 = User Selected (Typical Values = 10 kΩ to 100 kΩ)
Phase
Nonlinear
C1
C2
Linear
=
=
(
(
2
2
V
π
π
IN
)
)
(
Figure 69. Second-Order, Low-Pass Filter
(
1020Ω
f
f
. 1
R2
. 0
CUTOFF
CUTOFF
414
707
110pF
1020Ω
R1
C2
)
)
( )
( )
R1
R1
Amplitude (Pass Band)
Maximum flat
Equal ripple
Equal ripple
3
2
–13V
+13V
AD8610
7
4
U1
5
1
220pF
C1
6
V
OUT