Circuit and method for reducing voltage error when charging and discharging a variable capacitor through a switch

摘要

A circuit and method for reducing voltage error when charging and discharging a variable capacitor (44) through a switch (43). The switch (43) comprises a plurality of transmission gates (53-55) coupled in parallel. A control circuit (42) provides control signals for enabling transmission gates of the plurality of transmission gates (53-55). The control circuit (42) changes the resistance of the switch (43) by selecting an appropriate transmission gate wherein each transmission gate has a different resistance. The resistance of the switch (43) is varied as a capacitance of the variable capacitor (44) is changed to maintain a predetermined RC time constant over the entire range of capacitor values of the variable capacitor (44).