Automatic DC offset circuit ٩(͡๏̯͡๏)۶ ٩(͡๏̯͡๏)۶ ٩(͡๏̯͡๏)۶

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Analog

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Does anyone have a circuit that will give an automatic DC offset to an AC signal such that the AC signal's negative most swing just touches the 0V0 level?
 
Hi Analog,

google for auto-zero methods and adapt a cirucuit for your requirements.

Boncuk
 
Printed circuit Board is designed by prefessional electronic designer, maybe you should ask this question my site, it will be help with you.
 
Tap off the input via a resistor, feed to a cap with the other side of the cap going to ground and run the input and the cap/resistor combination to a differential amplifier.

When the input is at a stable voltage, the two inputs will be the same and the diff amp will be at zero output volts, if the input fluctuates then the diff amp will fluctuate accordingly less the DC value stored in the cap.

Size of resistor and cap depend on the frequency you're measuring.
 

hi picbits.
UIGC, what if the sine wave is centred on zero volts.?
ie: swinging thru zero.
 
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Pass - analogue electronics aren't my strong point but I've used the example above before for removing the DC offset for some automotive noise measuring applications and it worked fine.
 
Actually - rereading the original question I think I've got my wires crossed lol. Damn this lack of sleep.

My idea is to remove the DC offset rather than apply one to an AC input.

My bad.
 
picbits said:
Actually - rereading the original question I think I've got my wires crossed lol. Damn this lack of sleep.

My idea is to remove the DC offset rather than apply one to an AC input.

My bad.
Click to expand...

hi,
Sleep, whats that.?

What he is asking for sounds simple but its not that easy to implement.
 
First off we really need to know why he wants to do this, which may make everything a LOT simpler.

But (as an old idea) he might google "DC restoration" which was used in TV's year ago.
 
Nigel Goodwin said:
First off we really need to know why he wants to do this, which may make everything a LOT simpler.

But (as an old idea) he might google "DC restoration" which was used in TV's year ago.
Click to expand...

This is for providing automatic 100% modulation in a DSB+C transmitter. A diode clamp is a start, but it always will swing about -0v6 below ground because of the forward voltage drop factor. I would like to eliminate this issue.
 
Here is a circuit that should work. You may have to tweak component values, and you might want to put a pot in place of the GND on the base of Q3.
There are also op amp solutions.
 

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Here's a functional schematic of an op amp clamp which compensates for the drop of the diode. The diode drop is reduced by a factor equal to the open loop gain of the op amp. The output is thus clamped to the negative peak of the signal within approximately the ± op amp offset voltage.

R1 and C1 are selected to meet the frequency response and impedance requirements of the rest of the circuit including the op amp input bias current. D2 keeps the op amp from saturating on the positive signal, thus improving it's frequency response.
 
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