DC Restoration -- book?

[BottomTime]

Hello list members,

I have need to understand why DC restoration is required in a circuit. Can anyone here recommend a good book that explains DC restoration?

Also if you know of a good book (s) that cover complete circuits such as a system. I have plenty of books that cover the basic op-amp circuits, what I need is a book or two that explains how to put all of the building blocks together for "typical" audio systems.

Thank you,


Randy

[pinkmouse]

Hi Randy.

I'm probably just showing my ignorance here, but I have never heard of the term DC restoration. Can you amplify? (sorry )

As for the book, there may well be one, but I find it very informative just to go through any published schematics and try to work out what all the bits do, and break things down into modules I can understand. Much more fun than reading a dry textbook.

[azira]

Say you take an AC signal with a DC component on it. More precisely for this demonstration, you take 2-Volt P-P sin wave with 1-Volt DC offset so the signal swings from 2-Volts to 0-volts.

If you filtered this signal with an arbitrarily large capacitor, the resulting signal would have no DC component on it, ie a DC blocking cap in the digital world or "input cap" in many amps.

The signal now becomes a bipolar signal and swings from -1V to +1V.

But what if you wanted to restore that DC component, or in other words, level shift it so that it is no longer a bipolar signal. That's what a DC restorer circuit does.

I think they are used mostly in frequency modulated (with fixed amplitude) systems such as a TV or a radio where your input is naturally bipolar but you may only want one rail voltage in your circuit.

Since a DC restorer is going to take an input signal and restore a DC component at half the P-P amplitude if your input signals amplitude varies with time, the DC level of the input signal will also vary. This makes it fairly useless for an audio circuit.
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Danny