10k

OPA177

±10mV

Adjustment Range

100

100

100µA

1/2 REF200

100µA

1/2 REF200

V+

V–

R

G

INA118

Ref

V

O

V

IN

–

V

IN

+

INA118

www.ti.com

SBOS027A – SEPTEMBER 2000 – REVISED JANUARY 2016

Typical Application (continued)

Figure 27. Optional Trimming of Output Offset Voltage

8.2.2.4 Input Bias Current Return Path

Ω. However, a path must be

provided for the input bias current of both inputs. This input bias current is approximately ±5 nA. High input

impedance means that this input bias current changes very little with varying input voltage.

Input circuitry must provide a path for this input bias current for proper operation. Figure 28 shows various

provisions for an input bias current path. Without a bias current path, the inputs float to a potential which exceeds

the common-mode range of the INA118, and the input amplifiers saturates.

If the differential source resistance is low, the bias current return path can be connected to one input (see the

thermocouple example in Figure 28). With higher source impedance, using two equal resistors provides a

balanced input, with the possible advantages of lower input offset voltage due to bias current, and better high-

frequency common-mode rejection.

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