ECE

Sunday, 10 March 2013

THEVENIN TYPE 3

Find thevenin equivalent to the above circuit across ab

Solution

Connect a known current source or voltage source to the above circuit because without a independent source the circuit becomes inactive. So to make it active we are connecting a known current source or voltage source

From the above circuit V_TH = V₁

Applying nodal analysis at node V₁

Sunday, 10 March 2013 by Unknown · 0

Saturday, 9 March 2013

THEVENIN TYPE-2

Find thevenin equivalent of above circuit across terminal ab

Solution

For V_TH

Applying nodal analysis at node V₁

V₁-20 + V₁ + V₁ - V_TH = 0 --------------------------- 1

40 200 100

At node V₁

Saturday, 9 March 2013 by Unknown · 0

THEVENIN AND NORTON EQUIVALENT

THEVENINS

A linear network consisting of a number of voltage sources and resistances can be replaced by an equivalent network having a single voltage source called Thevenin’s voltage ( V_th) and a single resistance called Thevenin’s resistance (R_th ) .

NORTONS THEOREM

A linear network can be replaced by an equivalent network having a single current source called NORTON CURRENT ( I_n) is parllel to a single resistance called Norton resistance (R_n ) .

There are three cases in Thevenin (Norton )equivalent depending on the sources present in the circuit

by Unknown · 1

Thursday, 7 March 2013

QUESTIONS ON TRANSISTOR

1) What the output voltage of this transistor circuit will do (measured with reference to ground),if the potentiometer wiper begins at the full-down position (common with ground), and is slowly moved in the upward direction (closer to +V):

2) Complete the table of output voltages for several given values of input voltage in this common-collector amplifier circuit. Assume that the transistor is a standard silicon NPN unit, with a nominal base-emitter junction forward voltage of 0.7 volts:

Based on the values you calculate, explain why the common-collector circuit configuration is oftenreferred to as an emitter follower.

3) what the output voltage of this transistor circuit will do (measured with reference to ground),if the input voltage ramps from 0 volts to -10 volts (measured with respect to ground):

4) If we were to apply a sinusoidal AC signal to the input of this transistor amplifier circuit, the output would definitely not be sinusoidal:

It should be apparent that only portions of the input are being reproduced at the output of this circuit.The rest of the waveform seems to be ”missing,” being replaced by a flat line. Explain why this transistorcircuit is not able to amplify the entire waveform.

5)what is meant by the phrase, ”Class-A amplifier operation.” What does it mean for a particularamplifier circuit to operate in ”Class-A” mode?

Thursday, 7 March 2013 by Unknown · 0

Monday, 4 March 2013

TYPES OF CIRCUITS IN THEVENINS-1

Example:

Determine the Thévenin equivalent of the circuit below, as seen by the load, RL.

Solution

We want to create a Thévenin equivalent circuit of the circuit to the left of the terminals a-b.now separate R_L from the circuit and find R_th from terminals a-b

_Finding R_th.
Short circuit the current sources,open circuit the voltage sources

Now the circuit appears as follows

Monday, 4 March 2013 by Unknown · 0