# Doubt in working RC differentiator

Started by October 28, 2014
```Hey, I am a beginner in electronics ,
Will the RC differentiator... differentiate like in mathematics
Is THIS possible

Vi = sin2wt  , Vo = 2cos2wt .. mathematically differentiation of sin2wt will give 2cos2wt...... (Vo= differerential (Vi))

IF we design a RC diff ... to satisfy equation
RC= 0.0016T
where R and C are values of resistor capacitor respectively
and T ( Time period of the wave)  = (2*pi)/w
If we change the value of the w to 2w  ;  (sinwt will be sin2wt)

will the AMPLITUDE DOUBLES ......as per the mathematical expression ( relation)

using this can we obtain a higher magnitude of differentiated input as output

And is it possible to produce 20Vpp ( peak to peak voltage) spikes as output from 10Vpp input sine wave with a clipper to create square wave from sine wave
```
```On Tue, 28 Oct 2014 07:33:44 -0700 (PDT), Abhijith M
<abhijith.newton@gmail.com> wrote:

>Hey, I am a beginner in electronics ,
>Will the RC differentiator... differentiate like in mathematics
>Is THIS possible
>
> Vi = sin2wt  , Vo = 2cos2wt .. mathematically differentiation of sin2wt will give 2cos2wt...... (Vo= differerential (Vi))
>
>IF we design a RC diff ... to satisfy equation
>RC= 0.0016T
>where R and C are values of resistor capacitor respectively
>and T ( Time period of the wave)  = (2*pi)/w
> If we change the value of the w to 2w  ;  (sinwt will be sin2wt)
>
>
> will the AMPLITUDE DOUBLES ......as per the mathematical expression ( relation)
>
>using this can we obtain a higher magnitude of differentiated input as output
>
>And is it possible to produce 20Vpp ( peak to peak voltage) spikes as output from 10Vpp input sine wave with a clipper to create square wave from sine wave

The RC acts almost as a differentiator at frequencies way below the
corner frequency. The corner freq is 1/(2*pi*RC).

Well above the corner frequency, the transfer function is 1, because
the cap acts as a short. So an RC doesn't make voltage gain.

An LC can make voltage gain near its resonant frequency.

There is a weird RCRC circuit that has a small voltage gain. I once
accidentally made an oscillator that way, when I was trying to make a
pseudo-inductor.

--

John Larkin         Highland Technology, Inc

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

```
```On Tue, 28 Oct 2014 07:33:44 -0700, Abhijith M wrote:

> Hey, I am a beginner in electronics ,
> Will the RC differentiator... differentiate like in mathematics Is THIS
> possible
>
>  Vi = sin2wt  , Vo = 2cos2wt .. mathematically differentiation of sin2wt
>  will give 2cos2wt...... (Vo= differerential (Vi))

Like John said -- the RC differentiator only approximates a mathematical
differentiator.

> IF we design a RC diff ... to satisfy equation RC= 0.0016T where R and C
> are values of resistor capacitor respectively and T ( Time period of the
> wave)  = (2*pi)/w
>  If we change the value of the w to 2w  ;  (sinwt will be sin2wt)
>
>
>  will the AMPLITUDE DOUBLES ......as per the mathematical expression (
>  relation)
>
> using this can we obtain a higher magnitude of differentiated input as
> output

Nope.  Not with just an RC.

> And is it possible to produce 20Vpp ( peak to peak voltage) spikes as
> output from 10Vpp input sine wave with a clipper to create square wave
> from sine wave

Are you trying to do this to power a circuit, or do you need to do this
to a signal for some reason?

There are many ways to attain your goal, but which one is best (or even
feasible) depends on what your sine wave comes from (and it's frequency),
and you want to do with your square wave once you have it.

--
www.wescottdesign.com
```
```On 2014-10-28, Abhijith M <abhijith.newton@gmail.com> wrote:
> Hey, I am a beginner in electronics ,
> Will the RC differentiator... differentiate like in mathematics
> Is THIS possible

The RC differentiator is only approximate, and only gets close to
ideal at frequencies much lower than 1/(RC) at higher frequencies it
behaves like (and is called) a high-pass filter.

> using this can we obtain a higher magnitude of differentiated input as output

not with a sine wave input, but a square wave can give spurs
approaching twice the input amplitude (measured peak-to-peak)

> And is it possible to produce 20Vpp ( peak to peak voltage) spikes
> as output from 10Vpp input sine wave with a clipper to create square
> wave from sine wave

not using RC, but there's many other ways to do that.

--
umop apisdn

```
```On 10/28/2014 9:33 AM, Abhijith M wrote:
> Hey, I am a beginner in electronics ,
> Will the RC differentiator... differentiate like in mathematics
> Is THIS possible
>
>   Vi = sin2wt  , Vo = 2cos2wt .. mathematically differentiation of
> sin2wt will give 2cos2wt...... (Vo= differerential (Vi))

Before going any further, please go back to your high school calculus
book and learn to differentiate.

If Vi = sin(2wt), then the derivative (with respect to t) is dVi =
2wcos(2wt)dt. Then think about what this means. It does not imply a
change in amplitude. It says that the derivative of Vi (your so-called
output) is the rate of change of the Vi with respect to time (t).

> IF we design a RC diff ... to satisfy equation
> RC= 0.0016T
> where R and C are values of resistor capacitor respectively
> and T ( Time period of the wave)  = (2*pi)/w
>   If we change the value of the w to 2w  ;  (sinwt will be sin2wt)
>
>
>   will the AMPLITUDE DOUBLES ......as per the mathematical expression
> ( relation)
>
> using this can we obtain a higher magnitude of differentiated input as
> output
>
> And is it possible to produce 20Vpp ( peak to peak voltage) spikes as
> output from 10Vpp input sine wave with a clipper to create square wave
> from sine wave
>

```
```Hey Guys..
It was a question asked for our collage lab practicals ...I just wanted to know if its possible of not...
We shouldn't use amplifiers too.
so.. a friend of mine came up with an idea to use a transistor as a switch for a higher required voltage
controlled by the input sine wave
there by creating a pulse train for positive peaks of sine wave and then differentiating it to produce spikes

sine waves maybe from signal generators..

and thanks to all those helped me... :)

```
```Hey guys ..
That question was asked in our collage lab practicals...
Anyway thanks for helping me ....
BTW... We were told not to use amplifiers ...so A friend of mine thought ab=
out an idea to use transistor as a switch ..,to provide an external supply =
sufficient to produce an output required for the differentiator.., to produ=
ce spikes of required output.., by using input sine waves positive halfs as=
control for switch( the output of switch will be square pulse of almost sa=
me frequency as input halfs which on differentiation will produce required =
spikes)
we hadn't tried it ..from theory it seems possible...=20
Sine waves are produced using signal generators...

Thanks :)
```