Op-Amp

• Why Does an Op Amp Have a High Input Impedance and a Low Output Impedance?

  • Op Amp is a Voltage Gain Device. Op amps have high input impedance and low output impedance because of the concept of a voltage divider, which is how voltage is divided in a circuit depending on the amount of impedance present in given parts of a circuit. Op amps are voltage gain devices. They amplify a voltage fed into the op amp and give out the same signal as output with a much larger gain. In order for an op amp to receive the voltage signal as its input, the voltage signal must be dropped across the op amp.

    • For the same reason of a voltage divider, an op amp needs a low output impedance. Once the voltage is dropped across the op amp and it does its task of amplifying the signal, the signal should get dropped across the device that the op amp should feed.

  • To Prevent Loading. Another reason op amps need high input impedance is because the loading effect. If op amps had very low input impedance, it would draw significant amounts of current into it. Thus, it would be a large load on the circuit. The fact that an op amp has a high input impedance ensures that it consumes very little current from the circuit and doesn't cause a loading issue in the circuit in which it demands and sucks up large amounts of current of the circuit.

• Input Impedance of an Amplifier and How to Calculate it

• Inverting Operational Amplifier - The Inverting Op-amp

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