Operational Amplifiers (Opamps)

The introduction of the μA741 operational amplifier (opamp, op-amp, op amp) integrated circuit in 1968 significantly changed the analog design philosophy from on where every amplifier circuit was designed with individual transistor amplifiers, to a more "packaged" approach. Due to the opamp's unique characteristics (see below), it became possible to apply simple formulas to standard configurations for creating many circuits. There are many "cookbooks" available that contain hundreds of configurations covering everything from simple amplifiers to complex filters, differentiators, integrators, multi-break-point frequency responses, even logarithmic amplifiers.

Standard nodal analysis can be used to perform opamp circuit analysis, including the properties of superposition. Here are a few of most often found opamp configurations that are found either by themselves, or as part of more complex circuits.

Ideal opamps assume the following properties:

  * Infinite open loop gain
  * Zero output impedance
  * Infinite input impedance
  * Infinite bandwidth

Non-Inverting
Equation Operational Amplifier Non-Inverting OpAmp - RF Cafe

 - RF Cafe
Inverting
Operational Amplifier Inverting OpAmp - RF Cafe

Equation Operational Amplifier Inverting OpAmp - RF Cafe
Buffer
Operational Amplifier Buffer OpAmp - RF Cafe


Equation Operational Amplifier Buffer OpAmp - RF Cafe
Differentiating
Operational Amplifier Differentiating OpAmp - RF Cafe

Equation Operational Amplifier Differentiating OpAmp - RF Cafe

At any single frequency
the gain is:

Equation Opamp Differentiating Voltage Frequency -  RF Cafe
Integrating
Operational Amplifier Integrating OpAmp - RF Cafe

 Equation Operational Amplifier Integrator OpAmp - RF Cafe

At any single frequency
the gain is:
Equation Opamp Integrating Voltage Frequency -  RF Cafe
Differential
Operational Amplifier Differential OpAmp - RF Cafe

 Equation Operational Amplifier Differential OpAmp - RF Cafe
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