8.1 Overview

The INA12x instrumentation amplifier is a type of differential amplifier that has been outfitted with input protection circuit and input buffer amplifiers, which eliminate the need for input impedance matching and make the amplifier particularly suitable for use in measurement and test equipment. Additional characteristics of the INA12x include a very low DC offset, low drift, low noise, very high open-loop gain, very high common-mode rejection ratio, and very high input impedances. The INA12x is used where great accuracy and stability of the circuit both short and long term are required.

8.2 Functional Block Diagram

8.3 Feature Description

The INA128-HT and INA129-HT are low power, general-purpose instrumentation amplifiers offering excellent accuracy. The versatile three-operational-amplifier design and small size make the amplifiers ideal for a wide range of applications. Current-feedback input circuitry provides wide bandwidth, even at high gain. A single external resistor sets any gain from 1 to 10,000. The INA128-HT and INA129-HT are laser trimmed for very low offset voltage (25 μV typical) and high common-mode rejection (93 dB at G ≥ 100). These devices operate with power supplies as low as ±2.25 V, and quiescent current of 2 mA, typically. The internal input protection can withstand up to ±40 V without damage.

8.4 Device Functional Modes

8.4.1 Noise Performance

The INA128-HT and INA129-HT provide very low noise in most applications. Low-frequency noise is approximately 2 μVPP measured from 0.1 Hz to 10 Hz (G ≥ 100). This provides dramatically improved noise when compared to state-of-the-art, chopper-stabilized amplifiers.

G ≥ 100

Figure 19. 0.1-Hz to 10-Hz Input-Referred Voltage Noise