Connect with us

Help With an Equation

Discussion in 'Electronics Homework Help' started by ashesv14, Apr 21, 2014.

Scroll to continue with content
  1. ashesv14

    ashesv14

    5
    0
    Feb 10, 2014
    The equation is to find the resistor value for the inverter
    Vout is 0.1V and Vdd is 5V.

    ratio of the resistance are:

    Vout/Vdd = 0.1/5 = (Rds/(RL+Rds))

    or RL = 49Rds

    Can I have a explanation how RL=49Rds, where Vout=0.1V and Vdd=5V
     
  2. LvW

    LvW

    604
    146
    Apr 12, 2014
    I am afraid, there is no help possible without some additional information.
    *What kind of inverter (opamp or transistor)?
    *What is RL and Rds ?
    *What kind of "equation"? Gain?
     
  3. hevans1944

    hevans1944 Hop - AC8NS

    4,536
    2,112
    Jun 21, 2012
    You take the equation(0.1/5) = 0.02 = (Rds/(RL+Rds)) and use algebra to solve for RL = 49Rds. There are usually limits (a range of suitable values) for Rds. Plug one in and multiply by 49 to get RL.
     
  4. Merlin3189

    Merlin3189

    250
    69
    Aug 4, 2011
    How about using ratios?:
    0.1/5 = 1/50 (making both numbers 10x bigger keeps the ratio the same)
    So RDS / (RDS + RL) = 1 / 50
    So whatever RDS is; 1 Ohm, 1 kOhm, 1 lot of 270 Ohm, etc.
    then (RDS + RL) is 50 of them; 50 Ohm, 50 kOhm, 50 lots of 270 Ohm (ie. 13.5kOhm), etc.
    The RDS is one of them, so RL must be 49 of them: in math language, RL is 49 x RDS

    As Hevans says, you can use algebra to show that
    RL is RDS multiplied by (one less than ( Vdd divided by Vout) )
    or rearrange to find any other one of the values.
    You can put all the known numbers into a formula which is any way round, then the algebra becomes easier.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-