Datasheet

1 MW 50 kW
52.6316 kW
50 kW
2.7778 kW
1 MW
V
+IN
7
3
2
6
4 1
A1
INA148
–V
S
V
O
V
–IN
0.1 µF
+V
S
0.1 µF
V = (V – V )
O
+IN –IN
INA148-Q1
www.ti.com SBOS472A –MARCH 2009–REVISED OCTOBER 2011
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.
Figure 1. Basic Circuit Connections
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 operational amplifier (op amp) to "see" input voltages that are within its linear operating range. A "Tee"
network in the op amp feedback network places the amplifier in a gain of 20 V/V, thus restoring the circuit's
overall gain to unity (1 V/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 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
minimize noise pickup.
Operating Voltage
The INA148 is specified for ±15-V and ±5-V dual supplies and 5-V single supplies. The INA148 can be operated
with single or dual supplies with excellent performance.
The INA148 is fully characterized for supply voltages from ±1.35 V to ±18 V and over temperatures of –40°C to
125°C. Parameters that vary significantly with operating voltage, load conditions, or temperature are shown in the
Typical Characteristics section.
Gain Equation
An internal on-chip resistor network sets the overall differential gain of the INA148 to precisely 1 V/V. Output is
accordance with Equation 1.
V
OUT
= (V
+IN
– V
–IN
) + V
REF
(1) (1)
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Product Folder Link(s): INA148-Q1