Op-amp (ideal)

Ideal operational amplifier: the inputs are at equal voltage and draw no current.

  • electrical
  • Modelica Standard Library
  • 3 ports
BlockOp-amp (ideal)KindopAmpLibraryElectrical

Description

An ideal operational amplifier (nullor): the two inputs draw no current and are forced to the same voltage, and the output supplies whatever current that takes. Use it with external feedback resistors.

Example

Op-amp amplifiers Two inverting amplifiers: an ideal op-amp with a gain of −10, and a limited one that clips at its ±15 V rails.

1 V 50 HzR in 1 kΩR f 10 kΩIdeal op-ampv outGroundGround +1 V 50 Hz (limited)R in 1 kΩ (limited)R f 20 kΩLimited op-ampv out (limited)Ground (limited)Ground + (limited)
In Gradara, select a Op-amp (ideal) block and press F1, then choose Open example. It opens as a new model in My models, ready to run.

Also in this example:Voltage sensorGroundResistorOp-amp (limited)AC voltage

Ports

Conserving terminals 3

  • +in_pelectrical

    Non-inverting input. Draws no current.

  • −in_nelectrical

    Inverting input. Draws no current.

  • outelectrical

    Output pin. Its current is unconstrained; it returns through Ground.

Equations

Modelica
in_p.v = in_n.v
in_p.i = 0
in_n.i = 0

Implementation

Modelica Standard Library 4.1.0Modelica.Electrical.Analog.Ideal.IdealOpAmp3Pin
MSL documentation

Assumptions and limitations

  • No gain limit, output swing limit, bandwidth, offset, or current limit.
  • Only works with negative feedback. Without a feedback path to in_n, or with positive feedback, the circuit has no unique solution.

See also

Select a block in Gradara and press F1 to open its page offline.