Introduction So, we want to break down our continuous-time sigma-delta feedback into two paths: A low-precision tight loop that delivers the first sample to the quantizer A higher-precision loop that goes through a clock delay to minimize “metastability” (indecision)
Introduction The impulse invariant transform (IIT) is a method of taking a continuous-time system H(s) and converting it to a discrete-time system. There are multiple ways of doing this, but the IIT does so with the constraint that the impulse response of the discrete-time system is a sampled version of the impulse response of the […]
In a previous post, I discussed the trade-offs in linearity of several continuous-time sigma-delta schemes. In this post, I will describe a method that linearizes the sigma-delta noise-shaping filter (NSF). That is, the scheme presented in this article greatly suppresses the linearity requirements on the noise-shaping filter. This method applies to both discrete-time and continuous-time […]
The continuous-time sigma-delta (CTSD) analog-to-digital converter (ADC) is a class of sigma-delta analog-to-digital converters that utilize a continuous-time noise-shaping filter (NSF | H(s)). In this post, I analyze a few noise-shaping filter (NSF) architectures that affect highly linear CTSD ADC’s.
One of the defining traits of analog CMOS designers is the ability to implement a common-mode feedback (CMFB) loop. When the input devices on a differential pair are all NMOS (or NPN), and the loads are either inductors or resistors, a common-mode feedback loop is unnecessary, because the output resistance of the differential pair is […]