+ Post New Thread
Results 1 to 3 of 3
  1. #1
    Full Member level 3
    Points: 1,008, Level: 7

    Join Date
    Jan 2018
    Posts
    159
    Helped
    1 / 1
    Points
    1,008
    Level
    7

    Output power, Drain Current versus multipliers

    Hi, I set Width(W) and Number of fingers (nf) for a transistor (in CS configuration) and found out it's drain current (Id) and output power (Pout)(Using HB simulation) for a particular load resistance(R). Now, If I want the output power 8 times that of Pout, is it just enough if I take 8 multipliers without changing R ? and does that mean Drain current (Id) is also increased by 8 times?.

    •   AltAdvertisement

        
       

  2. #2
    Advanced Member level 5
    Points: 16,333, Level: 30
    pancho_hideboo's Avatar
    Join Date
    Oct 2006
    Location
    Real Homeless
    Posts
    2,497
    Helped
    665 / 665
    Points
    16,333
    Level
    30

    Re: Output power, Drain Current versus multipliers

    Can you surely understand "Instance Multiplier" ?

    Quote Originally Posted by circuitslave View Post
    If I want the output power 8 times that of Pout,
    is it just enough if I take 8 multipliers without changing R ?
    No.

    Can you surely understand "Impedance"and "Power" ?

    Show me your definition of input power.

    Quote Originally Posted by circuitslave View Post
    and does that mean Drain current (Id) is also increased by 8 times?.
    No.
    Surely consider operation point, input and output impedance.

    Surely learn and understand followings.
    https://www.edaboard.com/showthread....-any-technoogy

    https://www.edaboard.com/showthread....ime-in-Spectre

    https://www.edaboard.com/showthread....del-for-MOSFET
    Last edited by pancho_hideboo; 18th July 2019 at 15:02.



    •   AltAdvertisement

        
       

  3. #3
    Full Member level 3
    Points: 1,131, Level: 7

    Join Date
    Jan 2019
    Location
    Belgium
    Posts
    163
    Helped
    69 / 69
    Points
    1,131
    Level
    7

    Re: Output power, Drain Current versus multipliers

    You would get 8 times the drain current at DC no doubt. Now imagine you have managed to bias everything in class A. Then your current swing will be 8 times higher. 8 times current swing x same R --> ideally you should get 8 times the voltage swing. But you will be limited by your supply voltage. Typically, a PA is designed such that at the peak point, your voltage swing amplitude equals the supply voltage (I assume you have used an inductance between the drain and supply). So for the same resistance, you will not get 8 times the voltage swing. You will clip and will end up with power in higher harmonics.
    So, you need to change your input matching network so that you see 8 times lower resistance.
    But that is not the end of it. Now because your transistor is 8 times larger, your capacitance will increase as well. For optimum power matching, you need to change the value of the capacitance and inductance.

    In short, the answer is NO. Resources pointed out by pancho_hideboo are really excellent and you should go through them.



--[[ ]]--