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E252 Lesson 1 - Coggle Diagram

- - - - PNP
        
        Formula
        
        VIN1 and VIN2 are grounded (𝑉_𝐵=0).
        
        Using Ohms Law, 𝑰𝑹𝑬=(𝑽𝒄𝒄−𝑽𝑬)/𝑹𝑬
        
        Assume the transistors are well matched and large β,
        
        𝑰𝑬=𝑰𝑹𝑬/𝟐
        
        𝑰𝑪=𝑰𝑬
        
        𝑰𝑩=𝑰𝑪/𝜷
        
        𝐼𝑅𝐶=𝐼𝐶⇒ 𝑽𝑹𝑪=𝐼𝑅𝐶 𝑅𝐶=𝑰𝑪 𝑹_𝑪
        
        Using KVL, 𝑽𝑪=𝑽𝑬𝑬+𝑽_𝑹𝑪
        
        VOUT1 = VOUT2 = VC
      - NPN
        
        VIN1 and VIN2 are grounded (𝑉_𝐵=0).
        
        Using Ohms Law, 𝑰𝑹𝑬=(𝑽𝑬−𝑽𝑬𝑬)/𝑹𝑬
        
        Assume the transistors are well matched and large β,
        
        𝑰𝑬=𝑰𝑹𝑬/𝟐
        
        𝑰𝑪=𝑰𝑬
        
        𝑰𝑩=𝑰𝑪/𝜷
        
        𝐼𝑅𝐶=𝐼𝐶⇒ 𝑽𝑹𝑪=𝐼𝑅𝐶 𝑅𝐶=𝑰𝑪 𝑹_𝑪
        
        Using KVL, 𝑽𝑪=𝑽𝑪𝑪−𝑽_𝑹𝑪
        
        VOUT1 = VOUT2 = VC
    - - Differential amplifier is used to amplify the differential component of the input signals, however the common component of the input signals will also appear at the output.
        
        In practice, this common mode component will cause an error in the measurement of the signals.
        
        AC analysis is performed to find out these system responses:
        
        Differential Mode Gain : Adm
        
        Common Mode Gain : Acm
        
        Common Mode Rejection Ratio : CMRR = |Adm|/|Acm|
        
        To analysis its differential mode, the transistors are redrawn in equivalent t-model, and the following equations are obtained:
        
        AC emitter resistance, 𝒓𝒆=𝑽𝑻/𝑰𝑬 =𝟐𝟓𝒎𝑽/𝑰𝑬
        
        Differential Mode gain, 𝑨𝒅𝒎=𝑹𝑪/(𝟐𝒓_𝒆 )
        
        To analysis its common mode, it is obtained from “half circuits”:
        
        Common Mode gain, 𝑨𝒄𝒎=𝑹𝑪/(𝟐𝑹_𝑬 )
        
        The ratio of the differential gain and common mode gain is:
        
        Common Mode Rejection Ratio, CMRR =𝑨𝒅𝒎/𝑨𝒄𝒎
  - - - What is common in both inputs? Noise
      - What is different in both inputs? Voice
      - For a good amplifier:
      - Differential mode gain should be amplified
      - Common mode gain should be attenuated.
    - - Differential mode gain, Adm to the common mode gain, Acm
        
        (signal) (noise)
      - "CMRR"=|𝑨𝒅𝒎/𝑨𝒄𝒎 |
      - Thus CMRR shows how well the signal can be amplified and how well the noise is attenuated.
      - The main goal in circuit design is to minimize the noise level (or improve signal-to-noise ratio).
      - Thus, a large CMRR is desirable as it is less sensitive to noise. (CMRR>> 1). Since the CMRR can be a large number, it is often expressed in decibels or dB.
      - "CMRR" ("dB" )=𝟐𝟎〖"log" 〗"10" |𝑨𝒅𝒎/𝑨_𝒄𝒎 |