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Design >> Analog Design >> compare DC voltages
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Message started by aaron_do on May 23^rd, 2007, 12:24am

Title: compare DC voltages
Post by aaron_do on May 23^rd, 2007, 12:24am

Hi all,

I have a peak detector which gives me the signal level (Vin), but even without a signal, it outputs a DC voltage (Voffset). So the output is Vin+Voffset. Now I want to accurately compare Vin with a reference voltage, Vref. So i need some way to remove VOffset, or add Voffset to Vref. Anybody got any ideas?

thanks,
Aaron

Title: Re: compare DC voltages
Post by krishnap on May 23^rd, 2007, 7:31am

Hi Aaron,

Can the Voffset be stored in capacitor when Vin is zero and this voltage can be added to vref,
or cancel the effective Voffset from the output? just a thought.

Regards,
Krishna

Title: Re: compare DC voltages
Post by loose-electron on May 23^rd, 2007, 5:38pm

Why not a comparator with switched capacitor methods to store the offsets?

If it is a sampled time system that works well.

Otherwise, AC coupling thru the signal of interest (if you can define the spectrum, or is this truly a DC system?) is a possible, a dummy peak detector with no signal applied to provide an equivalent zero signal offset and op-amp differencing the two is possible, or a feedback system to remove the DC offset is another possibility.

Lots of options.

Title: Re: compare DC voltages
Post by aaron_do on May 23^rd, 2007, 8:48pm

thanks for all the replies.

i also thought about using a dummy peak detector with no signal applied, but the switched capacitor method is interesting...haven't done any SC circuit design yet though...