8

®

INA148

FIGURE 1. Basic Circuit Connections.

TYPICAL PERFORMANCE CURVES (Cont.)

At TA = +25°C, VS = ±15V, RL = 10kΩ to common, and VREF = 0V, unless otherwise noted.

APPLICATION INFORMATION

The INA148 is a unity gain difference amplifier with a high

common-mode input voltage range. A basic diagram of the

circuit and pin connections is shown in Figure 1.

To achieve its high common-mode voltage range, the INA148

features a precision laser-trimmed thin-film resistor network

with a 20:1 input voltage divider ratio. High input voltages

are thereby reduced in amplitude, allowing the internal op

amp to “see” input voltages that are within its linear oper-

ating range. A “Tee” network in the op amp feedback

network places the amplifier in a gain of 20V/V, thus

restoring the circuit’s overall gain to unity (1V/V).

External voltages can be summed into the amplifier’s output

by using the Ref pin, making the differential amplifier a

highly versatile design tool. Voltages on the Ref pin will

also influence the INA148’s common-mode voltage range.

In accordance with good engineering practice for linear

integrated circuits, the INA148’s power-supply bypass

capacitors should be connected as close to pins 4 and 7 as

practicable. Ceramic or tantalum types are recommended for

use as bypass capacitors.

The input impedances are unusually high for a difference

amplifier and this should be considered when routing input

signal traces on a PC board. Avoid placing digital signal

traces near the difference amplifier’s input traces to mini-

mize noise pickup.

OPERATING VOLTAGE

The INA148 is specified for

±15V and ±5V dual supplies

and +5V single supplies. The INA148 can be operated with

single or dual supplies with excellent performance.

The INA148 is fully characterized for supply voltages from

±1.35V to ±18V and over temperatures of –55ºC to +125 ºC.

Parameters that vary significantly with operating voltage,

load conditions, or temperature are shown in the Typical

Performance Curves section.

5

µs/div

INVERTING INPUT

50% OVERLOAD RECOVERY TIME

1M

Ω

50k

Ω

52.6316k

Ω

50k

Ω

2.7778k

Ω

1M

Ω

V

IN

7

3

2

6

41

A1

INA148

–V

S

V

O

+

V

IN

–

0.1

µF

+V

S

0.1

µF

V

O = (VIN – VIN)

–

+

5

µs/div

NON-INVERTING INPUT

50% OVERLOAD RECOVERY TIME

VS = ±15V

VIN–

VOUT

0V

0V

VIN+

VOUT

0V

VS = ±15V