Connect with us

voltage-controlled amplifier

Discussion in 'Electronics Homework Help' started by Bianca Nieuwenhuizen, Jul 20, 2010.

Scroll to continue with content
  1. Bianca Nieuwenhuizen

    Bianca Nieuwenhuizen

    4
    0
    Jul 20, 2010
    What is the correct way to costruct a working circuit containing an operational amplifier an a junction Field Effect Transistor, connected to a power supply and function generator to the circuit and perform gain measurements to requirements within twenty minutes? What am i required to do? How are the pins connected to the power supply? What are the restrictions and safety procedures?
     
  2. Bianca Nieuwenhuizen

    Bianca Nieuwenhuizen

    4
    0
    Jul 20, 2010
    Pleeease help!!!! I am supposed to write an report on a voltage controlled amplifier using operational amp 741 and a JFET 2N3819, one capacitor, between 1 & 10 microfarad, 1 variable resistor, and construct it later on, what are the safety procedures? How does this type of circuit work? How are the pins spicifically connected to the power supply? How does the gain work? Please i need help urgently, thank you!
     
  3. Ian

    Ian Administrator

    1,487
    435
    Aug 23, 2006
    Welcome to the forums Bianca, I have merged your two threads as they were on the same topic. Please just create one thread per topic in future :).

    As the notice at the top of this forum mentions, we can help you work through a problem - but we won't do the work for you. How far have you got on this problem and what is it that you don't understand about it?
     
  4. Bianca Nieuwenhuizen

    Bianca Nieuwenhuizen

    4
    0
    Jul 20, 2010
    I am sorry Ian, my apologies. well I would appreciate it if you maybe can just tell me where do I start searching. Our project is headed " Voltage-controlled amplifier", I would just like to know, where do I start searching for info on something like that, because I searched and the closest that I get to voltage controlled amps are info telling me that if you put 2 Jfets and 1 Op Amp together you will have voltage controlled amp. But my project only consists of One Jfet and an op amp. Well I know that an op amp is in the operation of an IC, correct? Point is if i can only know where to start, I'll know how to carry on form there? a hint or, maybe some basics to start with, will be greatly appreciated? THank you in advance!
     
  5. NickS

    NickS

    367
    0
    Apr 6, 2010
    I think the direction they want you to go in involves the Rds property of the JFET. They are not quite like other transistors. They are always sort of on. So think of the JFET as a variable resistor between drain and source. That resistance is controlled by the Vgs. So you have a voltage controlled resistor.

    Now where would you add a resistor to an op amp to control the gain? It may also help you to think about how the virtual ground will help your calculations.

    Hope that helps
     
  6. Bianca Nieuwenhuizen

    Bianca Nieuwenhuizen

    4
    0
    Jul 20, 2010
    thank you so much nick!! It helps allot!!:D
     
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

-