OP490
–18V
APPLICATIONS INFORMATION
Battery-Powered Applications
14
13
12
11
10
9
8
The OP490 can be operated on a minimum supply voltage of
1.6 V, or with dual supplies of
±
0.8 V, and draws only 60
mA
of
supply current. In many battery-powered circuits, the OP490
can be continuously operated for hundreds of hours before
requiring battery replacement, reducing equipment downtime,
and operating costs.
High performance portable equipment and instruments fre-
quently use lithium cells because of their long shelf-life, light
weight, and high energy density relative to older primary cells.
Most lithium cells have a nominal output voltage of 3 V and are
noted for a flat discharge characteristic. The low supply current
D
C
A
1
2
3
4
5
B
6
7
4
LITHIUM-SULPHUR DIOXIDE CELL VOLTAGE – V
GND
+18V
3
Figure 2. Burn-In Circuit
+15V
2
1/4
OP490A
1k
+15V
1
OP37A
V2
0
100
–15V
10k
0
250
500
750
HOURS
1000
1500
1750
Figure 4. Lithium-Sulphur Dioxide Cell Discharge Charac-
teristic with OP490 and 100 k
W
Loads
–15V
V
IN
1/4
OP490B
V1
20V p-p @ 10Hz
requirement of the OP490, combined with the flat discharge
characteristic of the lithium cell, indicates that the OP490 can
be operated over the entire useful life of the cell. Figure 4 shows
the typical discharge characteristic of a 1 Ah lithium cell power-
ing an OP490 with each amplifier, in turn, driving full output
swing into a 100 kW load.
V1
V2/1000
1/4
OP490C
CHANNEL SEPARATION = 20 LOG
Single-Supply Output Voltage Range
In single-supply operation the OP490’s input and output ranges
include ground. This allows true “zero-in, zero-out” operation.
The output stage provides an active pull-down to around 0.8 V
above ground. Below this level, a load resistance of up to 1 MW
to ground is required to pull the output down to zero.
In the region from ground to 0.8 V, the OP490 has voltage gain
equal to the data sheet specification. Output current source
capability is maintained over the entire voltage range including
ground.
Input Voltage Protection
1/4
OP490D
Figure 3. Channel Separation Test Circuit
The OP490 uses a PNP input stage with protection resistors in
series with the inverting and noninverting inputs. The high
breakdown of the PNP transistors coupled with the protection
resistors provides a large amount of input protection, allowing
the inputs to be taken 20 V beyond either supply without dam-
aging the amplifier.
REV. C
–9–
AD [ ANALOG DEVICES ]
