Device

47kW

47kW

Device

10kW

Microphone,

Hydrophone,

etc.

Thermocouple

Device

Centertapprovides

biascurrentreturn.

INA826

www.ti.com

SBOS562B

– AUGUST 2011 – REVISED DECEMBER 2011

INPUT BIAS CURRENT RETURN PATH

The input impedance of the INA826 is extremely high

—approximately 20 GΩ. However, a path must be provided

for the input bias current of both inputs. This input bias current is typically 35 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 61 shows various

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

the common-mode range of the INA826, and the input amplifiers saturate. If the differential source resistance is

low, the bias current return path can be connected to one input (as shown in the thermocouple example in

Figure 61). With higher source impedance, using two equal resistors provides a balanced input with possible

advantages of lower input offset voltage as a result of bias current and better high-frequency common-mode

rejection.

Figure 61. Providing an Input Common-Mode Current Path

Copyright

© 2011, Texas Instruments Incorporated

Submit Documentation Feedback

21

Product Folder Link(s): INA826