By Shanthi Pavan
There is an ever expanding development in the direction of placing complete structures on a unmarried chip. which means analog circuits should coexist at the comparable substrate besides tremendous electronic structures. considering applied sciences are optimized with those electronic structures in brain, designers must make do with ordinary CMOS approaches within the years yet to come. We deal with analog filter out layout from this angle. Filters shape very important blocks in functions starting from laptop disc-drive chips to radio transceivers. during this e-book, we boost the idea and strategies useful for the implementation of excessive frequency (hundreds of megahertz) programmable non-stop time filters in general CMOS approaches. seeing that excessive density poly-poly capacitors should not to be had in those applied sciences, substitute capacitor buildings must be came upon. Met- steel capacitors have low particular capacitance. another is to take advantage of the (inherently nonlinear) capacitance shaped via MOSFET gates. In bankruptcy 2, we specialise in using MOS capacitors as integrating parts. A physics-based version which predicts distortion properly is gifted for a two-terminal MOS constitution in accumulation. Distortion in those capacitors as a functionality of sign swing and bias voltage is computed. bankruptcy three studies continuous-time filter out architectures within the gentle of bias-dependent integrating capacitors. We additionally speak about the benefits and demerits of varied CMOS transconductance components. the issues encountered in designing excessive frequency programmable filters are mentioned in detail.
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Extra resources for High Frequency Continuous Time Filters in Digital CMOS Processes
The dynamic range of the simulations is about 100dB. 9 compare the levels of second and third harmonic currents in the capacitors. 10 shows variation in distortion components as a function of signal level for two different values of capacitor bias. 9. 17 Third harmonic relative to fundamental(– PWL, ⊕ proposed). 10. Harmonics relative to fundamental for different values of bias voltage(– PWL, ⊕ proposed). 11. Qualitative C-V curves of a MOS capacitor with n+ and p+ polysilicon gates. Since an n-type substrate is assumed, accumulation is to the right of the minimum on each curve.
CMOS transconductors are compared based on several performance parameters. In the last section of this chapter, we discuss the additional problems that arise when filters have to be programmed over a wide range. 2. 1. In practice, the response deviates from the ideal at low frequencies due to finite DC gain and at high frequencies due to parasitic poles and zeros. 1, where a high frequency parasitic pole is assumed. A convenient method of evaluating integrator performance is in terms of its quality factor, QI (w).
Turning things upside down, we now say that the quality factor of the pole forming section is the reciprocal of the imaginary part of the denominator polynomial (also called the characteristic polynomial) at that frequency at which the real part is zero. 3. 9: Expanding the above, we get If the parasitic poles are far removed from w0, an approximate value for w at which the real part of D'(jw) goes to zero is w0. 4. 37 A MOSFET-C integrator The effect of nonideal integrators is to modify the quality factor of the biquad.