Transistor AMPLifier HelP !!!!

Discussion in 'General Electronics Chat' started by sudar_dhoni, Dec 3, 2009.

  1. sudar_dhoni

    Thread Starter Member

    Nov 9, 2009
    could some1 explain it entire circuit in terms of electron movement i.e how the voltage drops in each component in terms of electron flow

    1)i cant understand the voltage divider bias i find it extremely difficult
    plz explain it interms of electron movement in any one of the circuit diagrams mentioned below (explain the voltage drops for the electron current

    2)also to be frank i cant understand what basically Vbe and Vce is
    is it the barrier voltage between base emitter and base collector respectively
    if so then how can voltage drop occur at CB junction
    it experiences no impedance and only attraction then how can the voltage drop there
    what is meant by emitter base juction has less resistance and collector base junction has high resistance.But actually electrons from emitter get attracted to the collector easily how come that region has high resistance

    i have posted the circuit diagram
    i have many doubts there about how the voltage drop between R1 and R2 gives forward bias to the base emitter
    also which current's voltage is getting dropped there
    in my diagram its showing collector current
    but collector current itself arises from the emitter
    also u have not biased the emitter till now then how did u get Ic

    forward bias provided by the voltage drop of Ic
    see u have not biased it and u r about to bias the emitter only from voltage drop of Ic
    then where did u get that Ic from
    Ic comes only after biasing EB

    so could some1 explain the entire circuit qualitatively in terms of electron current starting from the ground plz dont explain in terms of conventional current. I want only electron flow
    i want to know how can the voltage drop cause forward bias to the base emitter
  2. Audioguru


    Dec 20, 2007
    You do not need to look at electron flow.

    The datasheet for the transistor has a graph that shows that its base-emitter voltage at a collector current of 0.85mA is about 0.67V. The collector to emitter current will warm the transistor which will reduce the base-emitter voltage to about 0.65V. It doesn't matter how.

    Vce is the voltage from the collector to the emitter because current flows here when the base-emitter has current. Ohm's Law and the collector resistor sets the Vce.

    The collector base junction is not conducting here because it is reverse-biased.

    The transistor is an NPN. The collector is N type, the base is P type and the emitter is N type. The base-emitter junction is forward-biased and conducts current because the base is positive and the emitter is 0V.

    Please stop writing in TEXTSPEAK like ****** little kids do which is very hard to read. Please write in proper English.
  3. sudar_dhoni

    Thread Starter Member

    Nov 9, 2009
    i have a serious doubt about biasing a pn diode and npn transistor
    first i'll mention about pn diode biasing
    the basic doubt i have in pn diode is that
    during forward bias + is connected to P and - is connected to N (+terminal -terminal)
    what i read in hyperphysics is that the electrons in N type cross the holes and go to the positive terminal and equal electrons from negative terminal flows to the N type again
    in this way the diode forward bias explanation is convincing
    but what i read in this site
    is that the electrons first start from the negative terminal and go to N type and cross barrier potential and go to p type and go back to positive terminal
    in the latter explanation the pn junction is not anything special
    it is just like a ordinary small resistor dropping .7 volts.
    but the latter explanation is used everywhere even in rectifier they say diode does not allow current to pass from the battery in the other direction and allows the current to pass through it only in one direction
    then what is the use of inventing it calling it electronics devices
    nothing special is happening becuase no1 is explaining in terms of what is first happening in diode(my first explanation from hyperphysics).
    everywhere they are explaining in terms of electrons or current coming from the battery
    i want to know how rectifier bridge rectifier works i.e starting from the diode and not from supply. because if we start only from the diode we can say its electronics
    if we simply start from the supply its none other than simply electrical

    I have the same doubt in npn transistor
    to be frank i cant understand ur circuit
    basically i cant understand voltage divider bias
    plz what ever circuit u show me can u plz mark me the electron movement
    in this circuit i have many questions
    1)plz can u mark direction of electron flow
    2)the circuit is open how can current of electron flow
    3)i cant understand voltage divider bias i.e how can a voltage drop cause bias
    4)why Re ( resistance ) is used. in my book its mentioned stabilisation what is that
    5)why capacitor C1 is used
    6)major doubt
    from where does the electron flow start
    this one is making me mad
    in the working its given the electrons flow form emitter to base and to collector i.e its given it starts from the emitter
    but in single stage ce amplifier its give its statrs form Vcc and signal
    which is right?

    plz some1 clear my doubt
  4. sudar_dhoni

    Thread Starter Member

    Nov 9, 2009
    Hello Audioguru!!
    Are you asking me to put the necessary punctuation marks?
  5. Audioguru


    Dec 20, 2007
    Little kids write "ur" on their phones instead of "your" on a keyboard.

    It doesn't matter which way the electrons flow in a transistor amplifier.
    Simply forward-bias the base-emitter junction then a much higher current will flow in the collector to emitter. The datasheet of the transistor shows the base-emitter voltage at various currents and temperatures and shows the range of beta.