Method for amending the effect of offset voltage variations from the output voltage in a D/A converter
AssigneeNokia Mobile Phones Ltd.
InventorsRisto Vaisanen, Jukka Sarasmo
Life of this patent
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Abstract
The present invention relates to an offset voltage zeroing method of a D/A converter, with the aid of which oscillations of the output voltage of said D/A converter can be radically reduced. An output signal of the converter is carried to a first terminal of a capacitor (5). A second terminal of the capacitor is coupled to a reference voltage (V.sub.ref) with a controllable switch (6) as long as there are no pulses in the output of the converter. As a result, an amended output signal is obtained from the second terminal.
Claims6
A circuit for eliminating effects of offset voltage variations in pulsatile outputs appearing at an output of a digital to analogue (D/A) converter means, said circuit comprising:
- an input terminal and an output terminal, said input terminal coupled to said output of said D/A converter means;
- a capacitor connected in series between said input terminal and said output terminal;
- a reference potential source;
- switch means connected between said reference potential source and said output terminal;
- and
- control means connected to said switch means for causing said switch means to connect said reference potential source to said output terminal when no pulsatile output is present at said input terminal.
Dependencies are inferred from the claim text.