# Doubt in working RC differentiator

• posted

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

• posted

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 ```
• posted

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

Nope. Not with just an RC.

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```
• posted

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.

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

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

```--
umop apisdn```
• posted

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).
• posted

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... :)

• posted

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... Sine waves are produced using signal generators...

Thanks :)

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