How a transistor in common-base configuration amplify signal, Electrical Engineering

Q. With a circuit diagram explain how a transistor in common-base configuration amplify signals.

 The common-base terminology is derived from the fact that the base is common to the input and output sides of the configuration. Also the base is the terminal closest to ,or at, ground potential. The input characteristics for a transistor in common base configuration can be obtained by plotting a graph with VBE as x-axis and IE as the y-coordinate at various levels of output voltage VCB. Also the output  characteristics can be observed by plotting VCB along x-axis and IC along y-axis for various levels of IE.

The output or collector set of characteristics has three basic regions of interests : the active, cut-off and saturation regions. The active region is the  region normally employed for linear (undistorted) amplifiers. In the active region the base-emitter junction is forward biased, while the collector-base junction is reverse-biased. 

The signal to be amplified Vs is applied to the input leads, ie. between the emitter and the base. The electrons leaving the base take two paths. A small percentage combines with the holes in the base region and constitute the base current, while the majority of these diffuse towards the collector junction. The collector junction is reverse biased and these electrons can easily cross the junction and form the collector current. This collector current is allowed to pass through a high resistor connected in series with the collector. The voltage  developed across the load resistor is the amplified output voltage.

The amount of collector current depend upon the recombination at the base, the smaller the recombination the larger the collector current. A small base current controls large collector current. If the base-emitter voltage is increased slightly, more electrons are injected into the base region, which will be more than the base can use (recombination). This results in a larger collector current. In short, a smallchange in the base voltage cause very large change in the collector current. This is current amplification. The large collector current passing through the load resistor produces high voltage across which will be several times greater than the small input voltage applied to the input.

Posted Date: 6/11/2013 5:41:19 AM | Location : United States

Related Discussions:- How a transistor in common-base configuration amplify signal, Assignment Help, Ask Question on How a transistor in common-base configuration amplify signal, Get Answer, Expert's Help, How a transistor in common-base configuration amplify signal Discussions

Write discussion on How a transistor in common-base configuration amplify signal
Your posts are moderated
Related Questions
1) Consider the magnetic circuit shown in the figure. Steady currents flow in the windings of N 1 and N 2 turns on the outside legs of the ferromagnetic core. The core has a

Using Bode plot calculate (a) Phase margin (b) Gain margin (c) Stability of closed loop system. The open transfer function of the system is t=30/(s+2)/(s+3)Using Bode plot calcula

For the 3-bit 2 n -R D/A converter of Figure, calculate the analog output voltage when the input is (a) 100, and (b) 010. Solution a. For the binary input 100, switches con

SHLD Store HL pair Direct Instruction This  instruction is used to store the contents of HL  register  pair to  memory  address specified  in the  instruction and the  next ad

Q. Show limitations of microprocessor-based control systems? Practical limitations of microprocessor-based control systems stem from the following considerations: • Finite-w

Use of Capacitor in Technical Loss Reduction The use of capacitors to correct for poor power factor is a well-built and cost-effective means of reducing distribution system lo

what is ohm?

Draw the circuit diagram for  the  connections to the EPROM and  just one RAM device  as defined  in  the memory map in question  3. You must show all the connections required to o

Fly  Back Converter In fly  back  converter an inductor is used is  primary winding of transformer. Inductor  stores  the energy when  unregulated DC  input is given  to the