Chapter 1

Chapter 1

• Amplifier Models

• These are purely models, and cannot be replicated in a real world environment. They are meant to explain.
• Trans stands for transfer - from voltage to current or visa versa.
• The inputs and outputs can be either current or voltage. This leads to 4 amplifier models.
• You can use any of these models, though some may be easier to work with (if you are given the Thevenin or Norton equivalent)

Amplifier type Gain type Equation	Voltage input	Current input
Voltage output	Voltage Open-circuit voltage gain $A_{vo}={\frac {v_{o}}{v_{i}}}$	Transresistance Open-circuit transresistance gain $R_{moc}={\frac {v_{ooc}}{i_{i}}}$
Current output	Transconductance Short-circuit transconductance gain $G_{msc}={\frac {i_{osc}}{v_{i}}}$	Current Short-circuit current gain $A_{isc}={\frac {i_{osc}}{i_{i}}}$

1. Voltage
   1. To find the voltage-amplifier model for an amplifier, we must determine the open-circuit voltage gain, the input impedance, and the output impedance
2. Current
   1. "As before, the input resistance accounts for the current that the amplifier draws from the signal source. The output resistance is now in parallel with the controlled source and accounts for the fact that the amplifier cannot supply a fixed current to an arbitrarily high load resistance."
   2. To find the current amplifier model, we must determine the short-circuit current gain, the input impedance, and the output impedance
3. Transconuductance
4. Transresistance

• Definitions - ripped straight from the book
  • Input Resistance: $R_{i}$ of an amplifier is the equivalent resistance seen when looking into the input terminals
  • Output Resistance:$R_{o}$ is the Thevenin resistance seen when looking back into the output terminals of an amplifier
  • Open-circuit voltage gain: the ratio of output amplitude to input amplitude with the output terminals open circuited
  • Short-circuit current gain: the current gain with the output terminals of the amplifier short circuited

• Bag of Tricks
  • Buffer amplifier
  • Inverting amplifier