# Fundamental Physics/Electronics/Electronics Amplifier

## Electronics Amplifier

Electronics amplifier is an electronics device that provides voltage amplification . Electronics amplifier has a transfer function

${\displaystyle H={\frac {v_{o}}{v_{i}}}=\pm A}$

With

A - Amplification factor
the positive sign - means positive amplification . The circuit that provides positive amplification is called Non-inverting amplifier
the negative sign - means negative amplification . The circuit that provides negative amplification is called Inverting amplifier

## DC Amplifier

### Non-inverting amplifier

Using Op amp to provide positive amplification

${\displaystyle {\frac {v_{o}}{v_{i}}}=1+{\frac {R_{2}}{R_{1}}}}$
With ${\displaystyle R_{2}=AR_{1}}$ . ${\displaystyle v_{o}=Av_{i}}$

Using Transistor to provide positive amplification

${\displaystyle {\frac {v_{o}}{v_{i}}}=({\frac {R_{2}}{R_{2}+R_{1}}})({\frac {R_{4}}{R_{3}}})}$
With ${\displaystyle R_{1}=0.R_{4}=AR_{3}}$ . ${\displaystyle v_{o}=Av_{i}}$

Using Transformer to provide positive amplification

${\displaystyle {\frac {v_{o}}{v_{i}}}={\frac {N_{2}}{N_{1}}}}$
With ${\displaystyle N_{2}=AN_{1}}$ . ${\displaystyle v_{o}=Av_{i}}$

### Inverting amplifier

Using Op amp to provide positive amplification

${\displaystyle {\frac {v_{o}}{v_{i}}}=-{\frac {R_{2}}{R_{1}}}}$
With ${\displaystyle R_{2}=AR_{1}}$ . ${\displaystyle v_{o}=-Av_{i}}$

Using Transistor to provide positive amplification

${\displaystyle {\frac {v_{o}}{v_{i}}}={\frac {R_{2}}{R_{2}+R_{1}}}{\frac {R_{4}}{R_{3}}}}$
With ${\displaystyle R_{1}=0.R_{4}=(A+1)R_{3}}$ . ${\displaystyle v_{o}=-Av_{i}}$

Using Transformer to provide positive amplification

${\displaystyle {\frac {v_{o}}{v_{i}}}=-{\frac {N_{2}}{N_{1}}}}$
With ${\displaystyle N_{2}=AN_{1}}$ . ${\displaystyle v_{o}=-Av_{i}}$