Design Principles of Sample & Hold Circuits for Digital Audio Systems
Sample and Hold circuits are widely used in digital audio-systems and generally in signal processing and data conversion systems. High resolution analog-to-digital and digital-to-analog conversion modules require S&H-circuits for track-and-hold and deglitching. Sample and Hold circuits can cause various types of audio signal degradation: Aperture time is a (nonlinear) function of residual charge in the hold circuit; the error (clock jitter) and too short sampling intervals result in amplitude errors, the magnitude of this error increases with approaching the samplilng bound; Finite sampling pulse duration effects in conjunction with the order of the sample and hold circuit (zero- or first-order or polygonal hold) a frequency dependent transfer characteristic; Input-to-output and control-to-outut crosstalk causes additional errors. Most circuits apply MCSFETs for the sampling gate and the hold amplifier input stage, which limits the large signal characteristics and causes temperature effects. Design philosophy of sample and hold circuits requires a careful consideration of each possible error source.
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