30-01-2013, 04:45 PM
Lead-Lag Compensation
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Introduction
Among the simplest dynamic structures used in compensator design is the lead-lag compensator. A lead-lag
compensator has a transfer function of the form In this experiment, we will use the lead-lag structure to enhance the performance of an operational
amplifier. An op amp is different from the other control systems with which we are working this semester
in that it is a purely electrical device, operating over a relatively high range of frequencies and at low power
level. Nevertheless, compensator design problems for an op amp are mathematically similar to compensator
design problems for more conventional control systems such as a servomotor.
Operational Amplifier Model
In this experiment, you will be using the power amplifier from the previous experiments as the plant. Besides
the power supply, heat sinks, and miscellaneous hardware, the amplifier consists of an LM12 power op amp.
A close approximation to the actual response of the LM12 is given by the transfer function
Experimental Procedure
Throughout this experiment you may be faced with a variety of nonideal behaviors, such as noise, DC offset,
and amplifier distortion. These problems can be overcome by selecting your input signal level carefully.
Start by using the 0 − 2V range on the signal generator. Do not forget to scale by the input amplitude
when reading amplitude-related quantities like and When DC offset is observed, it is acceptable to
compensate for the offset by adjusting the vertical position of the oscilloscope trace.