Here is the most common Basic Circuits.
All the circuits posted here are Tested and verified under
i-St@r Laboratory
BS1.1 Bridge Rectifier
Working of the Circuit
# During the positive half cycle of secondary voltage, diodes D2 and D3 are
forward biased and diodes D1 and D4 are reverse biased Now the current
flows through D2-->Load-->D3
# During the negative half cycle of the secondary voltage, diodes D1 and D4
are forward biased and diodes D2 and D3 are reverse biased Now the current
flows through D4-->Load-->D1
# In both cycle the load current flows in same direction hence we get a
Pulsating DC voltage as shown in fig (2)
fig (1) Input Sine wave 
fig (2) Pulsating DC output# The capacitor is used for converting the pulsating DC voltage to fixed DC
voltage.
# Up to t=1s input is increasing, so the capacitor charged up to peak value of
the input. After t=1s input starts to decrease then the voltage across the
capacitor reverse biases the diodes D2 and D4 hence it will not conduct now
capacitor discharges through the load, then voltage across the capacitor
decreases
# When the peak voltage exceeds the capacitor voltage, Diode D2 or D4
forward biases accordingly as a result capacitor again charges to the peak
value. This process continues. Hence we get almost smooth DC voltage as
shown in fig (3)
fig (3) Constant DC output# i-St@r Tips:
You can use Step down Center tapped transformer as well as ordinary Step
down transformer. If you choose Center tapped transformer it is possible to
change the output DC.
By connecting middle point and a terminal point of transformer to the
rectifier or connecting both terminal points of transformer to the rectifier
circuit voltage can be changed.
BS1.2 Fixed Regulated Power Supply
# 78XX series available with output voltage of 5,6,8,9,12,15,18 and 24V.
# It give fixed output voltage.
BS1.4 RC Low Pass Filter/ Integrator
Low Pass Filter
#) Which allow to pass low frequency components and attenuates high
frequency components
#) The capacitive reactance Xc=1/(Cx2(pi)f).
#) That is capacitive reactance decreases with increase in frequency
#) Now at the high frequency, the capacitor act as a vertual short circuit which
directs the input signal to ground thus the output falls to zero
#) At low frequency, Capacitor acts as open circuit, and the entire signal
appear at the output
#) By observing above wave form we can see that the Amplitude decreases
when frequency increases
Integrator
#) Same circuit can be used as an Integrator
#) An Integrator does the mathematical operation 'Integration' on the input
signal
#) The time constant RC is very high as compared to time period of input
signal
#) When pulse waveform is applied to the circuit, capacitor charges through
the resistor abd hence the output voltage buildup
#) When the input is terminated capacitor starts to discharge.
#) Thus we get a Triangular waveform
#) As the value of RC increases amplitude of the output decreases (See above
fig) because it take more time to charge and discharge
BS1.5 RC High Pass Filter/ Differentiator
High pass filter
#) Which allow to pass high frequency components and attenuates low
frequency components
#) We know that the capacitive reactance Xc=1/C2(pi)F
#) That is capacitive reactance decreases with increase in frequency
#) Now at the high frequency, the capacitor act as a vertual short, Which
connect the iput to the output
#) At low frequency, the Capacitor acts as open circuit and it disconnects the
input and output terminals
#) By observing above wave form we can see that the Amplitude increases
when frequency increases
Differentiator
#) Same circuit can be used as an Integrator
#) A Differentiator does the mathematical operation 'Differentiation' on the
input signal
#) The time constant RC is very small as compared to time period of input
signal
#) The differentiated ouput is propostional to rate of change of input signal
#) If the rate of change of input signal is positive, then the output also
positive
#) When input remain maximum or minimum, output remain zero because the
rate of change of input is zero
#) Thus we got a Spike Wave form
#) As the value of RC increases amplitude of the output decreases (See the
fig) because it take more time to charge and discharge
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