# Help designing a circuit

• Engineering
• felipe_damascena

#### felipe_damascena

Summary: I want to design an electronic circuit that takes an sine wave as input and output a different wave

I want to design an electronic circuit that takes a sine wave as input(Vi) and it outputs a different wave (Vo). Vi goes from +5V to -5V

Vo is constant with the value of three, when Vi goes from 0V to 5V,
Vo goes from 3V to -2V, when Vi goes from 5V to 0V
Vo is constant with the value of -2, when Vi goes from 0V to -5V
V0 goes from -2V to 3V, when Vi goes from -5V to 0V

How can I do this?

<< Mentor Note -- thread moved to the schoolwork forums from the EE forum, so no schoolwork Template is shown >>

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Hi there
welcome to PF

Summary: I want to design an electronic circuit that takes an sine wave as input and output a different wave
How can I do this?

Well it would help if you were specific ... what sort of output wave ?
square?
sawtooth?
triangular ?
maybe even a sine wave that is out of phase with the input one ?

when you have decided the answer to that, then do some google searching

eg ... sine in square out
google sine to square wave converter circuit

come back and let us know what you find for what you want to do, post links or a circuit you find
and we here can give recommendations as to if it will do what you want

cheers
Dave

Why do you want to design the circuit?

Is the frequency of the sinewave variable or specified?
There are many solutions to the problem. What technology do you want to use?

The reason I want to design this circuit is for college, I am learning about electrics and electronic circuits. The teacher did not say what we should use to solve it, but i believe we should only use resistors, capacitor, inductors, diode and transistors. I have attached a file with the input wave and the output wave. I have studyed about clippers and clampers circuits up until now and I have no idea how can I make this circuit

#### Attachments

• circuito_2.pdf
85.4 KB · Views: 124
The reason I want to design this circuit is for college, I am learning about electrics and electronic circuits. The teacher did not say what we should use to solve it,
Welcome to the PF, Felipe. Schoolwork questions go in the Homework Help section of the PF, so I've moved your thread for you.

FYI, your written description of the circuit doesn't match the waveform you posted. Assuming that the waveform is correct (because a circuit that does what you described would be very complicated!), then this is a straight forward application of a clamping circuit, which you say you have studied.

"How can I do this" isn't a great question for homework help. I could just tell you the answer, but then what would you have learned. I presume that your instructor has shown you some examples of clamping circuits. Compare those to this problem.

What are your thoughts about an approach to this solution? What specifically is confusing you?

Finally, here's a hint: The circuit behaves very differently for large input amplitudes (above or below zero) than it does for smaller input amplitudes, so there is probably some dramatic change in the circuit when the input reaches the value where the circuit's behavior changes. Resistors and voltage/current sources don't change dramatically (we call these behaviors constant or linear), you will need to have some components that will change their I-V behavior significantly at some point to implement this function (we call these non-linear).

felipe_damascena and berkeman
What specially confuses me is how the wave changes his behavior when the input wave has 0V, because a diode can make the voltage constant, but only for values bigger or smaller than a certain voltage. In this output wave, when the input wave goes from 0V to 5V, the output wave has one behavior and when the input goes from 5V to 0V, the behavior changes and I do not know what kind of element can make this happen.

... and I do not know what kind of element can make this happen.
Clues: Voltage comparator, electronic switch, transmission gate, differentiator.

A sinewave has 4 quadrants. You have 4 rules.
Make a table of the rule to apply in each quadrant; 0, 1, 2, 3.

You will need two “bits” of digital information to select the quadrant.
Is the sinewave positive or negative?
Is the sinewave rising or falling?
How can you determine the quadrant from that information?

How can you design circuits to generate those two bits.

Clues: Voltage comparator, electronic switch, transmission gate, differentiator.

A sinewave has 4 quadrants. You have 4 rules.
Make a table of the rule to apply in each quadrant; 0, 1, 2, 3.

You will need two “bits” of digital information to select the quadrant.
Is the sinewave positive or negative?
Is the sinewave rising or falling?
How can you determine the quadrant from that information?

How can you design circuits to generate those two bits.
... level shift, clamp, ...

If precision is not required, like post #4 attachment ...
I have found a circuit that requires;
1 resistor.
2 capacitors.
3 diodes.
2 voltage sources.
That might not be the minimum possible.

I was finally able to find an answer too, this is my circuit in the falstad. What do you guys think?

Well done. Your circuit appears to meet the requirements using AC coupling and voltage clamps.

I note that your diode current is limited only by i = c * dv/dt of the input frequency.