The golden rules of op-amp behaviour
By DarthVader
Date: 2024-12-22
Topic: 220 see comments
Post views: 73
The golden rules of op-amp behaviour
Two so-called golden rules can be used to determine the gain of an op-amp
(Horowitz and Hill, 2015). These rules describe the behaviour of the op-amp,
and they are a direct consequence of its internal circuitry. They provide a
quick and easy way for an experienced designer to evaluate the behaviour of
op-amps inside feedback loops.
These rules can be stated as follows:
1.
In a closed loop, the output attempts to do whatever is necessary to make
the voltage difference between the inputs V+ and Vā equal to zero.
2.
The inputs draw no current, i.e. negligible (almost zero) current flows
between V+ and Vā.
For most applications, these two rules are sufficient to produce a draft
schematic (although when designing high-precision circuits, engineers also
need to use a software tool for simulation of analogue circuits).
Although the rules may appear strange the first time you read them, with a
little practice they become easy to use. Some common architectures and
applications of the golden rules will illustrate this.
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