Abstract
Since the amplifier is often the first signal processing stage in a system, it is likely that it may be subjected to the highest levels of disturbance, although the signal level at its input is still low. The signal-to-error ratio (ser) may therefore be degraded severely and these losses in ser can not be compensated adequately by other signal processing stages. Therefore, this work concentrates on presenting design strategies for negative-feedback amplifiers with reduced emi susceptibility. Moreover, it is assumed that the subsequent signal processing stages are less susceptible to disturbances, and that the disturbance level in these stages is lower.
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Notes
- 1.
Practical resistors, capacitors and inductors also show non-ideal behavior, specifically at higher frequencies. Their non-ideal behavior is extensively dealt with in textbooks, e.g., (Meijer 1996; Goedbloed 1993; Ott 2009), to which the interested reader is referred. Possible nonlinear behavior of passive components, e.g., electrolytic capacitors are not investigated, but may be analyzed with the methods presented in this work.
- 2.
When the current domain channel is evaluated, the same approximation for the bandwidth of the interconnect is found. The assumptions are now: \(Z_2\) is ideally zero, and when not zero much smaller than \(Z_1\). \(Z_1\) is for simplicity also taken equal to the source resistance \(R_s\).
- 3.
Practical amplifiers do not have either zero or infinite input impedance, but values much lower or higher than \(Z_0\) can be expected. Therefore, reflections will still occur.
- 4.
The same convention as in Sinnema (1988) is used. High impedance or parallel resonant comparable transfers are called anti-resonant, whereas low impedance or series resonant comparable transfers are called resonant.
- 5.
The low resistivity of conductors cause a low value of \(R\) at dc, which increases with \(\sqrt{\omega }\). Evaluation of the equations given in Table 2.1 shows that even for small distances between the conductors, \(\omega L\) is found to be much larger than the frequency dependent part of the resistance.
- 6.
Plane wave coupling to other types of interconnects can be analyzed in the same way.
- 7.
Note that these recommendations are the opposite of the general case in which the intended signal has to be transferred and hence \(\alpha \) should be as low as possible.
- 8.
The model with the common-mode sources divided equally over both connectors as shown in Fig. 2.9b can also be used to determine common-mode to differential-mode conversion for other cases of imbalance, e.g., when \(Z_{in}\) is also loaded by an impedance at its top terminal.
- 9.
Kaden points out that the equations for the Kamindämpfung are accurate when \(l\) is larger than or of the same magnitude as \(r_0\).
- 10.
- 11.
For an electrically-small system holds \(\fancyscript{L} \le 0.1 \lambda \), resulting in a maximal wave number of \(2\pi /(10 \fancyscript{L})\).
- 12.
Comparison of both equations showed a deviation of less than 2 \(\%\) for short shields.
- 13.
At frequencies lower than the pole, the results of this equation are the same as will result from the transmission line approach (Smith 1977) that will be presented in Sect. 2.8.4. For frequencies where \(i_{sh}\) remains constant, it is overestimated with an amount dependent on \(h\). It was found that up to an \(h=\) 50 cm the overestimation is about 6 dB. Smaller heights result in smaller overestimations. This is acceptable.
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van der Horst, M.J., Serdijn, W.A., Linnenbank, A.C. (2014). Decreasing the Disturbance Coupled to Amplifiers. In: EMI-Resilient Amplifier Circuits. Analog Circuits and Signal Processing, vol 118. Springer, Cham. https://doi.org/10.1007/978-3-319-00593-5_2
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