Alskv2011 trainer kit experiment 6

priyanka pai

Other Parts Discussed in Thread: TL082

I am working on ALSKv2011 trainer kit provided by Texas to our college.

In experiment no 6 ie Voltage controlled Oscillator i am getting the desired amplitude and frequency but my output duty cycle is not 50%.

i am getting around 64%(ie UTP>LTP) duty cycle.

1.changing any values of R and C will only vary amplitude and/or frequency.

2.adding a voltage follower in feed back network is also not solving the problem.

3.i am getting 13 V p-p as output of my schmitt trigger.

4.i am not facing any problem if i use the integrator circuit of VCO.

5.Each part(schmitt trigger, multiplier and integrator) of the circuit individually is giving 50%

please give any solution to reduce the duty cycle to 50%

over 14 years ago

0 Harmanpreet Singh over 14 years ago

Prodigy 90 points

For what value of the frequency u have designed the circuit

0 priyanka pai over 14 years ago in reply to Harmanpreet Singh

Prodigy 75 points

the design suggest that we can design frequency

T/2>>2vss/SR

SR=13V/microsec

Vss=10V

T>>1/325000sec

f<<325kHz

we see no change in duty cycle is we change the frequency from 300Hz to 2.5kHz

0 priyanka pai over 14 years ago in reply to priyanka pai

Prodigy 75 points

please suggest me the exact value of operating frequency i am getting the output for all frequencies as we change the R and C values in simulation

0 Harmanpreet Singh over 14 years ago

Prodigy 90 points

The reason behind it is the parameters of the IC tl082 i performed this experiment and found that the +vsaturation and -vsaturation are not same.

+v saturation is 9.6v and -v saturation is 9.0V approximately .That is why the duty cycle is not exactly the 50% .The simulation softwares assumes the both same so that is why the practical and theoretical results are not same.for practical circuit I suggest to use series resistance of 10 ohm and the zener doides at the output of the circuit .In this case u are supposed to connect the zener doides of +/-5volts connected back to back between the output and the ground .This will give you the 50%duty cycle of output in the practical circuit.

CIRCUIT FOR THE PRACTICAL IMPLIMENTATION OF VCO GIVING OUTPUT OF 50%DUTY CYCLE.

0 Harmanpreet Singh over 14 years ago in reply to Harmanpreet Singh

Prodigy 90 points

Sorry for the inconvenience , the circuit i uploaded above is wrong , the correct circuit is given below

simulation waveforms

Data converters

Data converters forum

Alskv2011 trainer kit experiment 6