REV. C

OP490

–9–

1

2

34

5

67

14

13

12

11

10

98

–18V

+18V

GND

C

B

D

A

Figure 2. Burn-In Circuit

+15V

–15V

1k

+15V

–15V

V2

100

10k

1/4

OP490A

1/4

OP490B

OP37A

V1

1/4

OP490C

1/4

OP490D

20V p-p @ 10Hz

CHANNEL SEPARATION = 20 LOG

V1

V2/1000

Figure 3. Channel Separation Test Circuit

APPLICATIONS INFORMATION

Battery-Powered Applications

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

HOURS

4

3

0

0

1750

250

500

750

2

1

1000

1500

Figure 4. Lithium-Sulphur Dioxide Cell Discharge Charac-

teristic with OP490 and 100 k

W Loads

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 k

W load.

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 M

W

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

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.