Op-Amps, PWM and Ignition Coils Tutorial (Part 1/3)

In this episode (Part 1/3) Shahriar discusses methods for generating a pulse-width-modulated (PWM) signal entirely in the analog domain by employing operational-amplifiers (Op-Amps). A total of four op-amps from a single power supply are used in unity-gain negative feedback, astable positive feedback, integrator and open-loop comparator configurations. The theory of operation as well as measurement are also presented. This episode also includes a quiz. Please post your answers in the comment section.

As a final experiment, an ignition coil is used to generate in excess of 20k volts! The combination of the PWM circuit and the ignition coil provides a stand-alone fully analog high voltage power supply.

Category:

Science & Technology

Tags:

• operational amplifier
• op-amp
• pulse width modulation
• PWM
• ignition coil
• integrator
• comparator
• negative feedback
• positive feedback
• square wave generator
• triangular wave generator
• high voltage
• spark generator

[grimmfactor]

Excellent video. Can this project (the PWM part, not the high voltage) be done with pretty much any op-amp?

[TheSignalPathBlog]

@grimmfactor Yes, pretty much. Except that depending on the op-amp's unity gain bandwidth and slew rate, the maximum oscillation frequency would be limited.

[Jiraya12345]

I can only hope my classes are as interesting as these videos!

[TheSignalPathBlog]

@Jiraya12345 Where do you study?

[Jiraya12345]

@TheSignalPathBlog

Northeastern University. I only just finished freshman year, so we haven't done any REAL electrical engineering stuff yet.

[TheSignalPathBlog]

@Jiraya12345 That is great, I am sure it will get more interesting. If you were at Columbia NYC, you could have taken my class!

[ib9rt]

I know electrical engineers do it a lot, but throwing the Laplace domain at the integrator doesn't really help to explain how it works. Anyone who can routinely write down Laplace transfer functions is already far beyond the level you are teaching here.

[Khwartz]

:-bd I I don't know about OpAmp at all, but you made me succeed to understand the general system you present, so Very Well Done! and thanks a lot! :)

[MrNingxiaoyu]

Thx a lot for this Video, however the gain of the 2nd OpAmp should be A=-R2 / R1(1+SCR2), if the value of R1 and R2 are very close to each other, then they can be cancelled out.

[DannjellZ0r]

Have watched many of your videos, they are AWESOME. You are so talented and very good att explaining things. IMO, you're in class with the lectures from MIT! (I do not attend MIT, just watch their lectures on youtube)

[grimmfactor]

Can you please clarify your formula for calculating the frequency of your relaxation oscillator? I am just unsure about the last part of the denominator that relates to the voltage divider.