High-sensitivity delay cells and circuits of detecting threshold voltage

Abstract

A circuit configured to detect a threshold voltage includes a first delay circuit, a second delay circuit and a controller. The first delay circuit has a first sensitivity to threshold voltage of a transistor. The first delay circuit may be configured to generate a first output signal delayed with respect to the input signal by a first delay time that changes depending on the digital control code. The second delay circuit has a second sensitivity that is higher than the first sensitivity. The second delay circuit may be configured to generate a second output signal delayed with respect to the input signal by a second delay time. The controller may compare the first and second output signals and may generate a digital output code corresponding to the digital control code when the first delay time is equal to the second delay time to indicate the threshold voltage of the transistor.