## Overview of the INA126PA The **INA126PA** is a precision instrumentation amplifier designed by Texas Instruments (Burr-Brown line). It is a low-cost, high-accuracy solution for amplifying small differential signals, commonly used in bridge-based sensors and data acquisition systems. --- ### Key Specifications | Feature | Specification | | :--- | :--- | | **Input Channels** | Single Channel | | **Supply Voltage Range** | ±1.35V to ±18V (Single or Dual) | | **Quiescent Current** | 175 µA (Low Power) | | **Gain Range** | 5V/V to 10,000V/V | | **Package Type** | 8-Pin PDIP (Plastic Dual In-line Package) | | **Input Offset Voltage** | 250 µV max | | **Operating Temperature** | -40°C to +85°C | --- ### Pin Configuration The INA126PA uses a standard 8-pin layout. The gain is set by a single external resistor ($R_G$). | Pin Number | Name | Function | | :--- | :--- | :--- | | 1, 8 | $R_G$ | Gain Set Pins (Connect external resistor here) | | 2 | $V_{in-}$ | Inverting Input | | 3 | $V_{in+}$ | Non-Inverting Input | | 4 | $V-$ | Negative Power Supply | | 5 | Ref | Reference Pin (Sets output zero level) | | 6 | $V_{out}$ | Output Signal | | 7 | $V+$ | Positive Power Supply | --- ### Technical Characteristics 1. **Two-Op-Amp Design:** Unlike traditional three-op-amp instrumentation amplifiers, the INA126 uses a unique two-op-amp architecture. This reduces the quiescent current, making it ideal for battery-operated equipment. 2. **Gain Equation:** The gain $G$ is determined by an external resistor $R_G$ connected between pins 1 and 8. The formula is: $$G = 5 + \frac{80\text{k}\Omega}{R_G}$$ 3. **Low Offset & Drift:** It features laser-trimmed circuitry to ensure very low offset voltage and minimal drift over temperature changes. 4. **Wide Supply Range:** It can operate on very low voltages (±1.35V) up to industrial standards (±18V). --- ### Typical Applications * **Industrial Sensor Amplification:** Ideal for thermocouples, RTDs, and bridge transducers. * **Medical Instrumentation:** Used in ECG and EEG monitoring due to its high input impedance. * **Multi-Channel Data Acquisition:** Low power consumption allows for many units to be used on a single board without overheating. * **Portable Devices:** Low current draw extends battery life. --- ### Simple Implementation Code (Conceptual) If you are using the INA126PA with a microcontroller (like an Arduino) to read a sensor, the logic typically follows this flow: ```cpp // Example: Reading INA126 Output via ADC const int analogPin = A0; float vRef = 5.0; // Supply voltage void setup() { Serial.begin(9600); } void loop() { int rawValue = analogRead(analogPin); float voltage = (rawValue * vRef) / 1024.0; // Calculate original sensor signal based on Gain (G) // Sensor_Signal = voltage / G; Serial.print("Output Voltage: "); Serial.println(voltage); delay(500); } ```