Note: This is an analog circuit project presentation. You must consider safety measures while making the circuit to work practically. Here you must insert 10Ω resistor in series with all the variable resistor and the capacitor used for integrator.

E-mail: mashood.ahmad32@gmail.com

Function Generators

Group Members:

1. Haris Tayyab

2. Hashim Iqbal Mian

3. Mashood Ahmad

IntroductionFunction generators provide us with different types of waveforms with different amplitudes and at different frequencies

The waves provided commonly are:

•Sine wave

•Triangular wave

•Saw tooth wave

•Square wave

Goal:Our goal was to make a circuit that gives square wave and triangular wave with variations in amplitude and frequency.

Theme:We designed a Non-inverting Bi-stable multi-vibrator to generate square wave and an Integrator to integrate the square wave and get triangular wave.

Circuit Module Distribution

The circuit can be divided into three modules to make it understand:

1.Bi-stable multi-vibrator (for Square wave generation)

2.Integrator (for Triangular wave generation)

3.Non-inverting amplifier (for amplitude control of square wave)

Circuit diagram

Inverting amplifier (attenuator)

Bi-stable multi-vibratorIntegrator

Bi-Stable Multi-vibrator:

• Two stable states (L+& L-)

• vo=L+, when vi=VTH=-(R1/R2)L-

• vo=L-, when vi=VTL=-(R1/R2)L+

• R1=10 kΩ (variable)

• R2=4 kΩ (fixed)

• Both resistors to set the Thresholds which is actually amplitude of triangular wave

Iv

Vi (Vo of integrator) Vo

• Integrating the square wave to produce triangular wave.

• Triangular wave at the output is serving as trigger for B.M.

• The peak values of the triangular wave are VTH and VTL.

• R=1 MΩ (variable, theoretical design),(100 KΩ practically)

• C=0.01uF (Fixed)• C and R providing time constant

to reach thresholds.• Change R to vary frequency of

triangular wave

Integrator:

vi , vo of B.M.vo

+ -

L-

L+

VTH

VTL

L+/RL-/ R

tri wave

sq wave

Inverting Amplifier:

• This amplifier is basically acting as an attenuator

• R4=1 kΩ (variable feedback resistor)• R3=1 kΩ (fixed resistor)• Output of B.M. is square wave with

peak amplitudes as L+ and L-.• So for different amplitudes we need

to attenuate it.• The circuit attenuates the square

wave as closed loop gain –(R2/R1) will always be less than or equal to 1.

vi, sq wave vo, sq wave

Calculations and Limitations:

• First, we calculate the limitations of the triangular wave amplitude:

LR

R

2

1THV

LR

R

2

1TLV

•R1=10KΩ variable and R2=4KΩ fixed•When R2=R1, peak amplitude of triangular wave goes to L+.•If R1= 0Ω,amplitude of triangular wave is zero.•So peak to peak amplitude range of triangular wave is from zero to 2L+.•Caution:

When R1 becomes greater than R2 the output of integrator is also goes into either of the saturations.

Triangular wave amplitude:

• Square wave’s amplitude depends upon R3 and R4 as follows:

IvR

Rv

3

40

• R3=1kΩ is fixed. R4=1kΩ is variable.• When R4=0Ω, square wave’s amplitude is zero.• When R4=1kΩ, square wave’s peak amplitude is L+.• So square wave’s amplitude ranges from zero to 2L+.

Square wave amplitude:

• Now, we find frequency range.• Starting from the formula,

L

VVCRT

fTLTH2

1

• After some manipulations,

2

141

R

RCRT

f

Frequency variation:

• Making the equation simpler by choosing R2=4kΩ.

• Choosing C=0.01uF

• Finally, we chose R and R1 as variable resistors to vary frequency.

• Lower limit of the frequency was 25 Hz.• Upper limit can’t be defined as when any of the variable resistor’s

value is zero, frequency is infinity that is not possible.

Frequency variation:

Sine wave shaping network:

• Input is triangular wave.• Input is straight line.• Due to exponential relation of

the current in diodes, the straight line is converted into curve.

• As there are two diodes for positive cycle as well as negative cycle, the output will be approximately a sine wave with three segments.

Questions

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