in control system, why have so many device like transistor? Wat is them function?
The essence of a control system is feedback to control output. It may be positive or negative as described here:
It's not directly related to a transister but is rather a circuit configuration.
The transister is used primarily as an amplifier, that is, boosting a weak input to provide a more powerful output.
Here is one brief explanation:
Transisters are widely used in many circuits because of their efficiency....very low heat loss for example.....and fast response times..they replaced vacuum tubes which used a lot more power and could not be made nearly as small as solid state transisters.
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