REV. B
OP290
–7–
1
7
4
5
6
3
2
8
+18V
–18V
100k⍀
200⍀
100k⍀
1/2
OP290
1/2
OP290
Figure 2. Burn-In Circuit
APPLICATIONS INFORMATION
BATTERY-POWERED APPLICATIONS
The OP290 can be operated on a minimum supply voltage of
1.6 V, or with dual supplies of 0.8 V, and draws only 19 pA of
supply current. In many battery-powered circuits, the OP290
can be continuously operated for thousands of hours before
requiring battery replacement, reducing equipment downtime
and operating cost.
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 voltage
requirement of the OP290, combined with the flat discharge
characteristic of the lithium cell, indicates that the OP290 can
be operated over the entire useful life of the cell. Figure 1 shows
the typical discharge characteristic of a 1 Ah lithium cell power-
ing an OP290 with each amplifier, in turn, driving full output
swing into a 100 kΩ load.
INPUT VOLTAGE PROTECTION
The OP290 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 provide a large amount of input protection, allowing
the inputs to be taken 20 V beyond either supply without dam-
aging the amplifier.
SINGLE-SUPPLY OUTPUT VOLTAGE RANGE
In single-supply operation the OP290’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 MΩ
to ground is required to pull the output down to zero.
In the region from ground to 0.8 V, the OP290 has voltage gain
equal to the data sheet specification. Output current source capa-
bility is maintained over the entire voltage range including ground.
+15V
+15V
–15V
–15V
V2
V
IN
1k⍀
9k⍀
100⍀
10k⍀
V1 20Vp-p @ 10Hz
CHANNEL SEPARATION = 20 LOG
V1
V2/1000
1/2
OP290
A
1/2
OP290
B
OP37A
Figure 3. Channel Separation Test Circuit
APPLICATIONS
TEMPERATURE TO 4–20 mA TRANSMITTER
A simple temperature to 4–20 mA transmitter is shown in Figure 5.
After calibration, the transmitter is accurate to +0.5°C over the
–50°C to +150°C temperature range. The transmitter operates
from 8 V to 40 V with supply rejection better than 3 ppm/V.
One half of the OP290 is used to buffer the V
TEMP
pins while
the other half regulates the output current to satisfy the current
summation at its noninverting input.
I
VRR
RR
V
RRR
RR
OUT
TEMP
SET
=
+
()
67
210
267
210
–
LITHIUM SULPHUR DIOXIDE
CELL VOLTAGE – V
100
80
0
0
60
40
20
350030002500500 1000 20001500
HOURS
Figure 4. Lithium Sulphur Dioxide Cell Discharge
Characteristic with OP290 and 100 k
⍀
Loads
The change in output current with temperature is the derivative
of the transfer function:
∆
∆
∆
∆
I
T
V
T
RR
RR
OUT
TEMP
=
+
()
67
210
