INA159 datasheet(22/51 Pages) TI2

22 / 51 page

Device

47kW

Device

10kW

Microphone,

Hydrophone,

etc.

Thermocouple

Device

Centertapprovides

biascurrentreturn.

INA826

SBOS562G – AUGUST 2011 – REVISED JUNE 2020

www.ti.com

Product Folder Links: INA826

Submit Documentation Feedback

8.3.5 Input Protection

The inputs of the INA826 are individually protected for voltages up to ±40 V. For example, a condition of –40 V

on one input and +40 V on the other input does not cause damage. However, if the input voltage exceeds (V–) –

2 V and the signal source current drive capability exceeds 3.5 mA, the output voltage switches to the opposite

polarity; see Figure 17. This polarity reversal can easily be avoided by adding resistance of 10 kΩ in series with

both inputs.

Internal circuitry on each input provides low series impedance under normal signal conditions. If the input is

overloaded, the protection circuitry limits the input current to a safe value of approximately 8 mA. Figure 17 and

Figure 18 illustrate this input current limit behavior. The inputs are protected even if the power supplies are

disconnected or turned off.

8.3.6 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 60 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 60). 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 60. Providing an Input Common-Mode Current Path

INA159 Datasheet(PDF) 22 Page - Texas Instruments