3D Visualization Of Better Decoupling Capacitor Placement

Placement matters: One way to decide how good a decoupling capacitor placement is by looking at the discharge current loop. Continue from previous post (http://electroniccircuitdesignsharing.blogspot.com/2012/07/3d-current-flow-for-inverting-op-amp.html), re-placing the decoupling capacitor near IC pin6 to bottom and just under supply pin will allow much better decoupling performance due to smaller discharge current loop. Compare diagrams below with the ones shown in previous post for details.

Top view of top signals

Top view of bottom signals

3D current flow for inverting op-amp with negative input pulse

I have always wanted to draw a 3-dimensional illustrative diagram on how the current flow – for the SMT circuit – with the Google Sketch up (mentioned in http://electroniccircuitdesignsharing.blogspot.com/2012/03/tools-for-circuit-design.html), finally I can create something shown in this post. Hopefully it is clear enough for you to understand how current flows after reading this.

Input and output voltages:

How the current flow – Inverting Amp with negative input pulse:

Top view of bottom signals:

Why Transfer Power At High Voltage

A friend once ask me why is it that the power transmission is always being done with high voltage, well, the reason is due to power transmission efficiency. As an example, supposed that we need to transfer 1 kilo Watt across some miles away, and the total cable resistance involves is 1Ohm, the efficiency calculation will be:

And plotting the graph shows that efficiency suffers as the voltage decreases.

As usual, more details are available in Wikipedia:

http://en.wikipedia.org/wiki/Electric_power_transmission

read through and have fun J

Debug - Op amp virtual ground probing with DMM

Watch out when probing op amp virtual ground, as the DMM loading will modify the feedback element of the inverting op amp. See http://electroniccircuitdesignsharing.blogspot.com/2012/05/feedback-loop-element-identification.html on how to identify the feedback element of inverting op amp.