Datasheet

8
®
INA148
FIGURE 1. Basic Circuit Connections.
TYPICAL PERFORMANCE CURVES (Cont.)
At T
A
= +25°C, V
S
= ±15V, R
L
= 10kΩ to common, and V
REF
= 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.
5µs/div
5V/div
INVERTING INPUT
50% OVERLOAD RECOVERY TIME
1MΩ 50kΩ
52.6316kΩ
50kΩ
2.7778kΩ
1MΩ
V
IN
7
3
2
6
41
A1
INA148
–V
S
V
O
+
V
IN
–
0.1µF
+V
S
0.1µF
V
O
= (V
IN
– V
IN
)
–+
5µs/div
5V/div
NON-INVERTING INPUT
50% OVERLOAD RECOVERY TIME
V
S
= ±15V
V
IN
–
V
OUT
0V
0V
V
IN
+
V
OUT
0V
V
S
= ±15V