Selected sample and hold circuits for the digital-to-analog conversion process

Signal processing for industrial control or automotive applications is done mostly on the digital level. The subsequent signal reconstruction process on the analog signal level often includes sample and hold-circuits. The paper investigates amplitude, phase and group delay behavior of the exponential and the polygonal hold, points out some peculiarities in amplitude and group delay close to the Nyquist frequency, compares the spectral distribution of the output signal for a sine input signal, and discusses the consequences for the implementation. The results for the exponential hold are applied to the widely used zero order hold, which (in the non-ideal case) can be considered as an exponential hold with a well defined-though comparatively small-time constant of the internal hold-capacitor charging circuit