AD8610ARM Analog Devices, AD8610ARM Datasheet - Page 14

• Manufacturer Part Number: AD8610ARM
• Description: Precision Very Low Noise Low Input Bias Current Wide Bandwith JFET Operational Amplifier
• Manufacturer: Analog Devices

AD8610
Although operating conditions imposed on the AD8610 (± 13 V)
are less favorable than the OPA627 (±15 V), it can be seen that
the AD8610 has much better drive capability (lower headroom to
the supply) for a given load current.
Operating with Supplies Greater than ± 13 V
The AD8610 maximum operating voltage is specified at ± 13 V.
When ± 13 V is not readily available, an inexpensive LDO can
provide ± 12 V from a nominal ± 15 V supply.
Input Offset Voltage Adjustment
Offset of AD8610 is very small and normally does not require
additional offset adjustment. However, the offset adjust pins can
be used as shown in Figure 24 to further reduce the dc offset. By
using resistors in the range of 50 kΩ, offset trim range is ±3.3 mV.
Programmable Gain Amplifier (PGA)
The combination of low noise, low input bias current, low input
offset voltage, and low temperature drift make the AD8610 a
perfect solution for programmable gain amplifiers. PGAs are often
used immediately after sensors to increase the dynamic range of
the measurement circuit. Historically, the large ON resistance of
switches, combined with the large I
created a large dc offset in PGAs. Recent and improved monolithic
switches and amplifiers completely remove these problems. A PGA
discrete circuit is shown in Figure 25. In Figure 25, when the 10 pA
bias current of the AD8610 is dropped across the (<5 Ω) R
the switch, it results in a negligible offset error.
When high precision resistors are used, as in the circuit of Figure 25,
the error introduced by the PGA is within the 1/2 LSB requirement
for a 16-bit system.
0.1
10
1
0.00001
0.0001
2
3
V
CC
–V
4
AD8610
S
LOAD CURRENT – A
+V
7
0.001
S
5
R1
V
EE
1
6
0.01
B
±
currents of amplifiers,
V
OUT
0.1
1
ON
of
1. Room temperature error calculation due to R
2. Full temperature error calculation due to R
3. Temperature coefficient of switch and AD8610 combined is
essentially the same as the T
High-Speed Instrumentation Amplifier (IN AMP)
The three op amp instrumentation amplifiers shown in Figure 26
can provide a range of gains from unity up to 1,000 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. 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 capacitance
does not reduce circuit bandwidth.
∆
∆
V
A0
A1
IN
V
V
OS
OS
Total Offset
Total Offset
Total Offset
∆
V
74HC139
/
/
G
A
B
∆
∆
OS
250
∆
T total
T total
V
(
(
Y0
Y1
Y2
Y3
=
OS
pA
I
(
B
5pF
@
100
)
)
×
×
85
=
=
=
=
=
R
15
5
AD
AD
°
∆
0 5
ON
C
.
V
µ
Ω
)
V
OS
8610
8610
µ
16
=
=
=
1
9
8
V C
+
/
2
3 75
I
∆
/
B
10
.
pA
T
° +
C
(
(
(
IN1
IN2
IN3
IN4
@
V
(
Offset
Offset Trimmed
pV
nV
AD8610
×
OS
85
12
–5V
5
+5V
4
0 06
V
ADG452
V
°
of the AD8610:
SS
Ω
≅
.
L
C
AD8610
)
_
5
+
)
=
GND
+5V
+5V
–5V
V
U10
nV C
DD
µ
×
10
∆
13
5
)
V
V
R
+
/
OS
pV
ON
° ≅
5
∆
S1
D1
S2
D2
S3
D3
S4
D4
V
(
ON
OS
@
)
ON
+
85
0 5
3
2
14
15
11
10
6
7
/
and I
∆
.
∆
°
T
and I
V
C
µ
(
10k
10k
100
V C
OS
1
)
1k
1k
11
B
B
=
/
:
°
B
×
:
G = 1
G = 10
G = 100
G = 1000
V
R
OUT
ON
)