The INA133 and INA2133 are high-speed difference amplifiers are designed for a wide range of general-purpose applications. Figure 7-2 shows the basic connections required for operation of the INA133. Place decoupling capacitors close to the device pins as shown in Figure 7-2 in applications with noisy or high impedance power supplies. All circuitry is completely independent in the dual version to provide lowest crosstalk and normal behavior when one amplifier is overdriven or short-circuited.

As shown in Figure 7-2, the differential input signal is connected to pins 2 and 3. The source impedances connected to the inputs must be nearly equal to maintain good common-mode rejection. A 5Ω mismatch in source impedance degrades the common-mode rejection of a typical device to approximately 80dB (a 10Ω mismatch degrades CMR to 74dB). If the source has a known impedance mismatch, an additional resistor in series with the opposite input can be used to preserve good common-mode rejection.

The internal resistors of the INA133 are accurately ratio trimmed to match. That is, R₁ is trimmed to match R₂ and R₃ is trimmed to match R₄. However, the absolute values may not be equal (R₁ + R₂ may be slightly different than R₃ + R₄). Thus, large series resistors on the input (greater than 250Ω), even if well matched, can degrade common-mode rejection.

Circuit board layout constraints can suggest possible variations in connections of the internal resistors, like that pins 1 and 3 can be interchanged. However, because of the ratio trimming technique used, CMRR can degrade. If pins 1 and 3 are interchanged, pins 2 and 5 must also be interchanged to maintain proper ratio matching.