INA826AIDR Layout and Selection Guide
09 April 2024
Ⅱ. Pin configuration and functions
Ⅲ. Functional features of INA826AIDR
Ⅳ. What impact does external resistance have on the stability of INA826AIDR?
Ⅴ. Schematic diagram and working principle of INA826AIDR
Ⅶ. Selection guide for INA826AIDR
The INA826AIDR is a cost-effective instrumentation amplifier with extremely low power consumption and the ability to operate over a wide single or dual supply range. The user can program any gain between 1 and 1000 with a single external resistor. With a gain drift of only 35 ppm/°C (max), the device provides excellent stability over temperature, even with gains greater than 1. The INA826AIDR is optimized to achieve excellent common-mode rejection ratio of over 100 dB (G = 10) at frequencies up to 5 kHz. At a gain of 1, its common-mode rejection ratio exceeds 84 dB over the entire input common-mode range, from the negative supply all the way to 1V of the positive supply. With its rail-to-rail output, the INA826AIDR is ideal for low-voltage operation, suitable for 3V single supply as well as dual supply environments up to ±18V. In addition, additional circuitry limits the input current to less than 8 mA, thereby protecting the input from overvoltages up to ±40V beyond the supply. The INA826AIDR is available in 8-pin SOIC, VSSOP and tiny 3 mm × 3 mm WSON surface mount packages and operates over the -40°C to +125°C temperature range.
Alternatives and equivalents:
• AD621BRZ
• INA128HD
INA826AIDR has 8 pins and comes in SOIC-8 package and tape and reel packaging. Below is its pin diagram:
Pin 1 (-IN): Negative (inverting) input
Pin 2 ~ 3 (RG): Gain setting pin. Place a gain resistor between pin 2 and pin 3.
Pin 4 (+IN): Positive (noninverting) input
Pin 5 (-VS): Negative supply
Pin 6 (REF): Reference input. This pin must be driven by low impedance.
Pin 7 (VOUT): Output
Pin 8 (+VS): Positive supply
INA826AIDR has following features:
1. Low power consumption: INA826AIDR adopts a low power consumption design with low operating current and is suitable for applications that require higher battery life.
2. Low noise: The INA826AIDR boasts minimal noise levels, facilitating precise signal amplification and transmission, making it ideal for high signal-to-noise ratio applications.
3. High bandwidth: INA826AIDR has high bandwidth and can transmit high-frequency signals, making it suitable for applications requiring high-frequency response, such as audio amplification and instrument measurement.
4. High precision: INA826AIDR has extremely low bias current and input bias voltage drift, and can provide high-precision differential amplification and signal transmission.
5. Differential input and output: INA826AIDR adopts differential input and output design, which can effectively suppress common mode noise and provide good anti-interference capability.
6. Wide input voltage range: INA826AIDR has a wide input voltage range and can support larger signal amplitudes, making it suitable for a variety of measurement and amplification applications.
First, the temperature coefficient of external resistors affects the stability of the INA826AIDR. Certain resistors will show a change in resistance value when the temperature changes, and this change may cause the amplifier gain to drift, thus affecting the stability. Therefore, when selecting external resistors, we need to consider their temperature coefficients and select resistors with lower temperature coefficients to improve the stability of the amplifier. Secondly, the accuracy and stability of the external resistor also directly affects the gain stability of the INA826AIDR. If the external resistor used has a large error or drift, then the gain of the amplifier will be affected accordingly, resulting in an unstable output signal. Therefore, the selection of high-precision, low-drift resistors is critical to improving the stability of the INA826AIDR. In addition, the selection of external resistors needs to take into account the influence of the supply voltage. The INA826AIDR performs well under low-voltage operation, but variations in the supply voltage may affect the performance of the amplifier. Therefore, when selecting an external resistor, we need to ensure that it maintains a stable resistance value even when the supply voltage changes, thus maintaining the stability of the INA826AIDR.
The working principle of the INA826AIDR device is based on the design of an operational amplifier. Its main function is to amplify weak signals while suppressing common-mode interference signals.
• Input protection: The input terminal of INA826AIDR has a protection function and can withstand input current up to 8 mA (other than the supply voltage). This helps protect the device from conditions such as overcurrent or short circuits.
• Input signal: The input signal of INA826AIDR is input through the -IN and +IN pins. These two pins receive weak signals from sensors or other sources. The instrumentation amplifier is designed to have high gain for differential signals while rejecting common-mode signals.
• Output signal: After amplification and filtering, the output signal is output from the VOUT pin. The output signal can be connected directly to subsequent signal processing circuits or data converters (such as ADCs).
• Power supply: The working power of INA826AIDR is input through the +VS and -VS pins. The device operates from a single supply voltage range of 2.7 V to 36 V or from a dual supply voltage range of ±1.35 V to ±18 V.
• Gain setting: The gain setting of INA826AIDR is achieved through external resistor RG. RG is connected between the RG pin and ground and is mainly used to set the gain of the amplifier. Its gain setting range covers a wide range from 1 to 1000. Specifically, the gain is directly proportional to the resistance of RG and inversely proportional to the parallel value of the internal resistors R1 and R2.
1. Layout guidelines
Attention to good layout practices is always recommended. Keep traces short and, when possible, use a printed circuit board (PCB) ground plane with surface-mount components placed as close to the device pins as possible. Place 0.1-μF bypass capacitors close to the supply pins. Apply these guidelines throughout the analog circuit to improve performance and provide benefits such as reducing the electromagnetic-interference (EMI) susceptibility. The INA826EVM is intended to provide basic functional evaluation of the INA826AIDR. An image of the INA826EVM is provided in the following figure. Attention to good layout practices is always recommended. For best operational performance of the device, use good PCB layout practices, including:
(1) Keep traces as short as possible.
(2) Place the external components as close to the device as possible.
(3) Route the input traces as far away from the supply or output traces as possible. This reduces parasitic coupling.
(4) Make sure to match both input paths to avoid converting common-mode signals into differential signals.
(5) Connect a bypass capacitor of 0.1-µF between each supply pin and ground, placed close to the device as possible.
(6) For the DRG package: Connect the exposed thermal pad to the lowest voltage potential on the circuit that is the negative power supply (–V).
2. Layout example
When selecting, we can pay attention to the following aspects to ensure that we choose the right device:
1. Temperature range
The operating temperature range of INA826AIDR is a limitation for its normal operation. When selecting, we should ensure that the ambient temperature of the amplifier is within its operating temperature range to ensure the stability and reliability of the amplifier.
2. Power supply range
The power supply range of INA826AIDR is the basis for its normal operation. When selecting, we should ensure that the power supply voltage provided meets the power range requirements of the amplifier to ensure the stability and reliability of the amplifier.
3. Stability
INA826AIDR focuses on stability during the design and manufacturing process to ensure its reliability and stability in various application scenarios. When selecting and using, we should pay attention to the stability indicators of the amplifier, such as long-term stability and temperature stability, to ensure that the amplifier can meet application needs.
4. Overvoltage protection
In order to protect the amplifier from overvoltage damage, the INA826AIDR usually has an overvoltage protection function. When selecting and using, we should understand the overvoltage protection characteristics of the amplifier and take corresponding measures in the circuit design to prevent overvoltage from causing damage to the amplifier.
5. Common mode suppression
INA826AIDR adopts a differential input design, which can effectively suppress common mode noise and interference. When selecting and using, we should ensure that the common mode component of the input signal is within the common mode suppression capability of the amplifier to obtain the best signal transmission effect.
6. Gain setting
The gain setting of INA826AIDR is a key step in its selection and use. Gain determines the amplification factor of the input signal by the amplifier, thereby affecting the signal transmission and processing effects. When selecting, we should determine the appropriate gain value based on the actual application scenario and needs. For example, for signal detection that requires high sensitivity, we need to choose a higher gain; and for applications that require reduced noise and distortion, we need to choose a lower gain.
Frequently Asked Questions
1. What is an amplifier?
An amplifier is an electronic device that increases the voltage, current, or power of a signal. Amplifiers are used in wireless communications and broadcasting, and in audio equipment of all kinds. They can be categorized as either weak-signal amplifiers or power amplifiers.
2. Can the INA826AIDR operate in single-supply configurations?
Yes, the INA826AIDR can operate in single-supply configurations when a reference voltage is provided.
3. What is the primary function of the INA826AIDR?
The primary function of the INA826AIDR is to accurately amplify small differential voltages in the presence of common-mode voltage.
