- The AD623 is an Instrumentation Amplifier with Rail to Rail feature. It also operates at a very low current of 550nA making it suitable for battery-operated applications.
Instrumentation amplifier:
- An instrumentation amplifier (sometimes shorthanded as in-amp or In Amp) is a type of differential amplifier that has been outfitted with input buffer amplifiers.
- These buffer amplifiers eliminate the need for input impedance matching and thus make the amplifier particularly suitable for use in measurement and test equipment.
Rail to rail Op-Amp:
- The output stage transistors prevent the amplifier from reaching the maximum positive voltage or minimum negative voltage.
- Therefore, the output pin of a normal op-amp will not be able to provide a voltage that is equal to the supply voltage.
- But the Rail to Rail Op-Amp overcomes this problem and hence the output pin can reach either positive rail voltage or negative rail voltage.
- Terms rail-to-rail input/output (RRIO) and rail-to-rail output (RRO).
- If an op amp can drive RRO, it means you have a good dynamic range in which to work on the signal. A related term, headroom, is a measure of how close the signal comes to the rails.
WORK of AD623
- The AD623 only requires a resistor to sets its gain value and hence can be easily set up. A very basic commonly used circuit for AD623 is shown below.
- The IC is powered using pin 7 and pin 4, here I have used a singly supply of +5V hence pin 4 is grounded.
- If a dual supply voltage is used pin 4 will be provided with negative voltage.
- The non-inverting pin (pin 2) and the inverting pin (pin 3) are connected to the signal which has to be amplified or compared based on the application of the Op-Amp.
- The Reference pin (pin 5) is normally grounded along with pin 4, the reference pin is used to direct the output towards a voltage when the difference voltage between the inverting and the non-inverting pin is 0V.
PIN Description
| PIN | PIN Name | Description |
|---|---|---|
| 1 | Gain (-Rg) | Inverting Gain Terminal connected to a resistor to set gain value |
| 2 | Inverting Input | The Inverting input pin of the Op-Amp |
| 3 | Non-Inverting | The Non – Inverting Input Pin of |
| 4 | Power (-Vs) | Negative supply terminal |
| 5 | Reference | Output reference input. Normally to common |
| 6 | Output | Amplifier output pin |
| 7 | Power (+Vs) | Positive supply terminal |
| 8 | Gain (+Rg) | Non-Inverting Gain Terminal connected to a resistor to set gain value |
Applications of AD623
- Low power medical instrumentation
- Transducer interfaces
- Thermocouple amplifiers
- Industrial process controls
- Difference amplifiers
- Low power data acquisition