Operational amplifier (Op amp) component

Op amp basic properties explained using LM358 diagram by electronzap
Op amp basic properties explained using LM358 diagram by electronzap

  • 2 inputs determine the output voltage
    • Inverting input
    • Non inverting input
  • Inputs just look at voltage. No current goes through them other than a tiny bit of leakage.
Single versus dual or split power supply using batteries pictorial by electronzap
Single versus dual or split power supply using batteries pictorial by electronzap
  • Output voltage of an op amp goes up if the non inverting input voltage is higher than non inverting input. Whereas output voltage goes down if non inverting input is lower than inverting input voltage. The output voltage stops at it’s limit of course, which is usually a volt or 2 shy of one or both supply voltages.
IC output voltage range illustrated for dual split supply single and rail to rail diagram by electronzap electronzapdotcom
IC output voltage range illustrated for dual split supply single and rail to rail diagram by electronzap electronzapdotcom
  • Dual supply op amp: Output falls short of either supply voltage. Operates best with a dual/split power supply where there is a positive and negative voltage in relationship to ground.
  • Single supply op amp: Output generally falls a volt or 2 shy of the positive supply, but can output the negative supply voltage, which is 0V ground in single supply circuits, and whatever the negative voltage is in relationship to 0V ground for a dual/slit supply. However, a load that needs current may still prevent the output voltage from dropping all the way to the negative supply.
  • Rail to rail: Output voltage goes all the way to both supply voltages (positive and negative). Again, loads that need current will likely prevent the output from getting all the way to the supply rail (positive and/or negative) voltage.

 

  • Output provides a limited amount of current. Some Op amps can provide more current than others. There is probably output short circuit protection. Always consult the datasheet for the specifics of the particular op amp you are interested in.
  • Feed back sends some or all of the voltage from the output back to one or both inputs. Doing so helps make the input voltage(s) closer to what the output voltage is. This is how you prevent the output from simply jumping straight to as close to either (positive or negative) supply voltages as it can go.

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