This paper presents an approach for the design ofa time stretcher based on charging and discharging a capacitorby currents with a ratio equal to the desired stretch factor. Thestretched time interval can be measured by using a time-to-digitalconverter to achieve improved system resolution. Expressionsfor the current source output impedance and transistor arearequired to reach a specified linearity and matching are derived.The realization uses wide-swing current mirrors to achieve therequired output impedance at an acceptable voltage swing at thecapacitor. The derived expressions and the overall design arevalidated with schematic and extracted simulations in a 0.35 μmCMOS process technology.