AD623 Instrumentation Amplifier & Its Working

An AD623 instrumentation amplifier is used in different electronics projects because of its different features like low power consumption; handling is simple, inexpensive, and uses three op-amps within one case. So, out of three op-amps, two op-amps are used to connect the positive & negative inputs whereas the third op-amp is used to display the output. This article discusses an overview of what is an AD623 instrumentation amplifier, pin configuration, specifications, features, circuit working, and its applications.

What is an AD623 Instrumentation Amplifier?

AD623 is one kind of instrumentation amplifier that is very simple to use. This kind of amplifier can be built with three op-amps. In this IC, the first two operational amplifiers are used for buffering the inputs whereas the 3rd operational amplifier is accountable for the output.

An instrumentation amplifier is one kind of differential amplifier that includes buffer amplifiers that are allied to their input pins. This removes the requirement of impedance matching, so it is suitable in test & measurement equipment.

AD623 Instrumentation Amplifier
AD623 Instrumentation Amplifier

This IC is used to amplify low range signals & reduces the extra noise as well as intrusion signals. In addition, it gives high input impedances through an adjustable gain feature. This type of IC is used to modify low-value signals and reduces the high noise distortion value within the signals to amplify. The input impedance value provided by this IC is better as compared to other amplifiers to improve its features.

In this type of module, the configuration of rail to rail op-amp exists and it does not provide voltage similar value toward the voltage given through the power source. It is because of o/p transistors that prevent the amplifiers from getting the maximum positive & least negative voltage. Instrumentation amplifiers are mainly formed throughout the normal amplifiers using resistance configuration & exist within IC form.

An op-amp’s normal output pin is not capable of providing a voltage that is equivalent to the voltage supply. So this is mainly due to the o/p stage transistors which avoid the amplifier from attaining the minimum negative or highest positive voltage. So, the Rail to Rail operational amplifier mainly conquers this difficulty and thus the output pin can arrive at either +ve rail voltage otherwise -ve rail voltage.

Pin Configuration of AD623 Instrumentation Amplifier

The AD623 instrumentation amplifier includes 8-pins where each pin and its functionality are discussed below. The pin configuration of an AD623 instrumentation amplifier is shown below.

AD623 Pin Out
AD623 Pin Out
  • Pins 01 & 08 (-, +): These are the inverting & non-inverting pins that are used to locate the amplifier’s gain by connecting an exterior resistor in between two pins.
  • Pins 02 & 03 (-IN, +IN): These two pins are the inputs for the amplifier.
  • Pins 04 & 07 (-Vs, +Vs): These two are the +Ve & -Ve power supply pins which provide single & dual supply operations
  • Pin05 (REF): The reference i/p is mainly used to set up the common-mode voltage for the o/p.
  • Pin 06 (Output): This pin is used to display the o/p of the instrumentation amplifier.

Specifications & Features

The specifications and features of the AD623 instrumentation amplifier include the following.

  • It is a rail to rail type instrumentation amplifier
  • It operates with a single & dual voltage supply
  • The maximum operating current is 550uA
  • Gain ranges from 1 – 1000
  • Bandwidth (BW) is 800KHz
  • Set gain through simply one resistor
  • Its performance is high
  • It includes fewer inputs & output voltage offsets.
  • Single supply voltage range is −Vs = 0 V, +Vs = 3.0 V – 12 V
  • It is available in different packages like 8-Pin SOIC, PDIP & VSSOP
  • The dual supply voltage ranges from ± 2.5 V to ± 6 V.
  • The current supply (maximum) for this IC is 550 µA.
  • The i/p voltage range extends for a single supply voltage like 150 mV underground.

How to use AD623 IC/Circuit Diagram

The AD623 instrumentation amplifier simply needs a resistor to fix its gain value. The common circuit diagram of an AD623 IC is shown below which is commonly used in different applications.

This IC can be activated through the two pins like pins 4 & 7. So in the above circuit, +5V of a single supply is used thus, the pin-4 of this IC is given to GND. Once the dual voltage supply is utilized then the pin-4 uses negative voltage.

AD623 IC Circuit Diagram
AD623 IC Circuit Diagram

Here, pin-2 is non-inverting and pin-3 is inverting pin which is used to connect the signal which has to be changed. The pin-5 is the Reference pin that is usually given to GND through pin-4. Here, the reference pin is mainly used to direct the o/p in the direction of a voltage once the difference voltage among both inverting & the non-inverting pins is equal to 0V.

The Op-Amp gain can be fixed by connecting the resistor’s correct value simply beyond the pin-8 (+Rg) & pin 1 (–Rg). In this circuit, a resistor with a 500Ω value is connected that will fix the operational amplifier at a 100 gain value. So, the following formulae are used to measure the gain value from resistor ‘R’ as shown below. Instead of this, we can also use different standard resistors and gain values

Where to use/Applications

The applications of the AD623 instrumentation amplifier include the following.

  • This IC possesses less noise, less DC offset & changeable gain that can be set through a single resistor.
  • This IC can be used in the circuits wherever high accuracy & stability are necessary.
  • The high input impedance of this IC will make this IC appropriate to use in equipment for measuring.
  • The high CMRR of this IC will make to use in an extensive range of different circuits.
  • It is applicable in low voltage based applications
  • By using this IC, different devices calibration can be done
  • Used in medical devices which use low power.
  • It is used where the sensitivity of power is necessary
  • Used in the modules of control system

Thus, this is all about an overview of an AD623 instrumentation amplifier datasheet which includes pin configuration, features, specifications, circuit working, and its applications. This AD623 Instrumentation amplifier includes a rail to rail feature and it functions at an extremely less current like 550nA so that it can be used in battery-operated applications. Here is a question for you, what is the main function of an instrumentation amplifier?

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