Programming instructions
National Instruments Corporation 5-1 Multisim Component Reference Guide
Chapter 5
Analog Components
5.1 Opamp
An ideal operational amplifier (Opamp) is an amplifier with infinite gain, infinite input
impedance and zero output impedance. With the application of negative feedback, Opamps
can be used to implement functions such as addition, subtraction, differentiation, integration,
averaging and amplification.
An opamp can have a single input and single output, a differential input and single output, or
a differential input and differential output.
5.1.1 Ideal Opamp Model
The ideal opamp model is the fastest to simulate. Its characteristics include:
• open-loop voltage gain (A)
The open-loop gain is the gain of the opamp without any feedback applied which in the
ideal opamp is infinite. This is not possible in the typical opamp, but it will be in the order
of 120 dB.
• frequency response
The frequency response of an opamp is finite and its gain decreases with frequency. For
stability, a dominant pole is intentionally added to the opamp to control this decreasing
gain with frequency. In an internally compensated opamp, the response typically is set for
-6dB/octive roll off with a -3dB frequency in range of 10 Hz. With an externally
ComponentRef.book Page 1 Thursday, December 7, 2006 10:12 AM