Key Facts from Reading Chapter 1

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The following facts are not profound and are possibly very obvious. Nonetheless, they might help cement certain concepts. Please add things you think would be helpful.


MOSFET diagram <ref> University of Cambridge </ref>
  • Conduction in n-type material is from free electrons.
  • Conduction in p-type material is from holes (positive particles).
  • The function of metal-oxide-semiconductor field-effect transistors (MOSFETs) depends on the voltage applied to the gate.
    • Certain ranges of voltage allow no current to flow between the drain and the source. In this way, the MOSFET acts like an open switch.
    • Another particular range of voltage allows current to easily flow from the source to the drain.
    • When the voltage is in between the ranges of open and closed switch, the MOSFET can smoothly control the amount of current flowing.
  • Bipolar Junction Transistors (BJTs) can act as either switches or current controls as well.


  • An inverting amplifier has a negative voltage gain, \ {A_{v}}.
  • A noninverting amplifier has a positive voltage gain, \  {A_{v}}. (If you get this, you deserve a cookie)
  • The power gain,\  G, is the ration of the output power to the input power
    • G=\frac{P_{o}}{P_{i}}=\frac{V_o{I_o}}{V_i{I_i}}=A_v{A_{i}}=(A_v)^2\frac{R_{i}}{R_{L}}
      • \ R_i is the amplifier's input resistance and \  R_o is the amplifier's output resistance.

Decibel Conversion

  • Power gain, \ G, can be converted to decibels:


\ G_{db}=10 log{A_{v}}^2+10 log R_i - 10 log  R_L

\ G_{db}=10  log |A_v|+10 log R_i - 10 log R_L

  • By the equation above, we can say voltage gain in decibels can be found with this equation: \ A_{v  dB}=20 log  |A_v|, where \  A_v is the voltage gain and \  A_{v  dB} is the voltage gain is decibels.
  • Similarly, we can say current gain in decibels can be found with this equation: \ A_{i  dB}=20 log  |A_i|, where \  A_i is the current gain and \  A_{i   dB} is the current gain in decibels.

Differential Amplifiers

  • Differential Amplifiers have two inputs. The terminal marked with a "+" is the noninverting input, and the terminal marked with a "-" is the inverting input.
  • The differential input signal is given by \  v_{id}=v_{i1}-v_{i2}
  • The output of an ideal differential amplifier is given by \ v_o=A_d  v_{id} .
  • The common-mode input signal is given by the following: v_{icm}=\frac{1}{2}(v_{i1}+v_{i2}).
  • A real differential amplifier's output is given by \   v_o=A_d v_{id}+A_{cm} v_{icm} , where \ A_{cm} is the common-mode signal gain.






  • The sentence that says "voltage gain and is the voltage gain is decibels." I think you mean "in decibels." Other than that nice work!