How do you know if a circuit is an amplifier?? Watch

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How do you know if a circuit is an amplifier from looking at the circuit diagram??
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(Original post by Lauren_F1)
How do you know if a circuit is an amplifier from looking at the circuit diagram??
The 'art' of electronics developed conventions for drawing circuits and experience will give one the knowledge to readily identify configurations and patterns in circuits.

When a basic configuration is identified, these can be assigned or labelled as a function rather like a building block.

There are a finite number of common 'patterns' or functional blocks and you once again with experience, you will start to look for the important components in the circuit which define critical performance parameters like gain or phase control or differential/integral functions, logarithmic functions, waveform shaping, different signal filtering techniques etc eyc.

It's then a case of analysing how those blocks of functions connect together and how they are interfaced with other devices to identify the full circuit function.

There are a finite number of basic amplifier blocks:

Very basic Integrated circuit Operational Amplifiers often look like this in circuit:

a) is the basic building block
b) is a unity gain, non-inverting buffer amplifier
c) is a non-inverting amplifier whose voltage gain is defined by the ratio of R1/R2
d) is an inverting version of c)
e) is a summing inverting amplifier whose function is defined by (R2/R1a) + (R2/R1b) +...(R2/R1x)

A basic discrete component version of the Operational Amplifier building block may look like:

Notice the labels for internal the various sections of the overall amplifier.

A commercial Operational Amplifier internal circuit may look like:

It's useful to compare the very basic circuit with the commercial version and you will see the same patterns emerging but in a more complex form (within coloured dotted lines).

The Op-Amp is a very important component in electronics but there are other equally important amplifiers which fall into several 'classes' defined by their different semiconductor biasing arrangement. Basic forms look like:

Class A looks like:

Class B:

Class AB (compare this with the above two circuits and also look at the additional components and notice there functions:

Class C:

Class D made up from building blocks:

There are others but progressively become more complicated and specialised.

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