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07-01-2025: Design of biasing
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Lecture: EE4109-13

Location: Pulse Hall 7 (33.A2.200)

Time: 15:45 - 17:30

.. image:: ../../../img/colorCode.svg
    :alt: color coded resistors

Biasing design considerations
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Biasing proceeds in two steps:

#. Design of the biasing with ideal voltage and current sources; this comprises the following actions:

   #. Biasing sources will be added to the transistors: four per transistor, as discussed in Chapter 3
   #. The power supply is added to the circuit
   #. Amplifier ports that should be referenced to the power supply are connected to one terminal of the power supply (called: signal reference)
   #. Bias current sources are redirected via the power supply, such that they can be impelemnted with passive elements
   #. The number of voltage sources in series with the signal path is minimized, by choosing N or P devices, by replacing CS with CD stages, or by changing the drain-source operating voltages

#. Design of the bias current and voltage sources

   #. A sufficiently accurate, stable and low-noise voltage or current reference (can be the power supply) is used as starting point for the design
   #. All other sources are derived from this reference, and their design procedure resembles that of an amplifier. 

      #. Define the requirements
      
         #. Architecture
         
            - Floating current source
            - Current source (connected to positive supply)
            - Current sink (connected to negative supply)
            - Floating voltage source
            - Voltage source connected to positive supply
            - Voltage source connected to negative supply
      
         #. Static V-I characterisics
         
            - Current source: current to be deliverd and voltage handling capability
            - Voltage source: voltage to be delivered and current handling capability
            - Accuracy, temperature stability
            
         #. Noise 
         
            Associated current noise or voltage noise in case of a current source or voltage source, respectively.
            
         #. Impedance
         
            - Small-signal source impedance
            - Parasitic impedances from floating terminals to signal reference (substrate)
            
      #. Find an operating principle
      
         - Voltage source character
         - Current source character
      
      #. Apply design techniques to improve performance/cost ratio
      
         - Negative Feedback
         - Compensation/Balancing
         - Filtering
         - etc.
         
Guided group exersise
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We will consider various biasing implementations for the single-stage and the dual stage solution of the hearing loop receive amplifier.

Please download the `Latest zip archive <../../designExample/HearingLoop/SLiCAPnotebooks/Vamp.zip>`_.