Datasheet

Device
47kW47kW
Device
10kW
Microphone,
Hydrophone,
etc.
Thermocouple
Device
Centertapprovides
biascurrentreturn.
INA826
www.ti.com SBOS562E –AUGUST 2011–REVISED APRIL 2013
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
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