8.4.1 First- or Second-Order Filtering

The output of the INA270 and INA271 is accurate within the output voltage swing range set by the power-supply pin, V+.

The INA270 and INA271 readily enable the inclusion of filtering between the preamp output and buffer input. Single-pole filtering can be accomplished with a single capacitor because of the 96-kΩ output impedance at PRE OUT on pin 3, as shown in Figure 16a.

The INA270 and INA271 readily lend themselves to second-order Sallen-Key configurations, as shown in Figure 16b. When designing these configurations consider that the PRE OUT 96-kΩ output impedance exhibits an initial variation of ±30% with the addition of a –2200-ppm/°C temperature coefficient.

NOTE:

Remember to use the appropriate buffer gain (INA270 = 1.4, INA271 = 2) when designing Sallen-Key configurations.

Figure 16. The INA270–INA271 can be Easily Connected for First- or Second-Order Filtering