 Oct 2018

www.shure.com www.shure.com

If the SM58 noise floor is calculated at room temperature, the voltage output is 0.00000032 volts.
This is equal to 130 dBV. The SM58 Vocal Microphone Specification Sheet says:
Sensitivity (at 1,000 Hz Open Circuit Voltage) –54.5 dBV/Pa (1.85 mV)
At this sensitivity, the selfnoise would be 94  (54.5  130) = 19 dB SPL, which is pretty typical and certainly not "lower than can be typically measured".

 May 2018

www.radioelectronics.com www.radioelectronics.com

plus the impedance of the path from the inverting input to ground i.e. R1 in parallel with R2.
This is incorrect. If R1 is infinite and R2 is 0, the parallel impedance is 0 ohms, but the input impedance is much higher than the input impedance of the opamp itself, due to feedback making the inputs very similar in voltage.
The input impedance is actually
$$(1 + A_0 B)\cdot Z_\mathrm{ino}$$
where
 \(A_0\) is the gain without feedback (the open loop gain)
 \(B\) is the fraction of the output which feeds back as a negative voltage at the input
 \(Z_\mathrm{ino}\) is input impedance without negative feedback
For the above buffer example, it would be close to \(A_0 Z_\mathrm{ino}\)
See https://electronics.stackexchange.com/q/177007/142
Simpson  Introductory electronics for scientists and engineers section 7.2 Negative Voltage Feedback explains this clearly

 Apr 2018

web.mit.edu web.mit.edu

10–27
Equation 1027 is wrong:
 Resistors are in parallel, their noise does not sum.

Adding this and the 100kΩ resistornoise to the amplifier noise
This is 3 terms (10 MΩ noise, 100 kΩ noise, and amplifier noise), but the equation only includes 2.

10–25
Equation 1025 has several errors:
 The left and right side are not equal.
 Resistors are in parallel, so their noise does not sum.
 Resistor noise needs to be multiplied by gain to be combined with 113.1 μV output noise of opamp.

10–23)
Equation 1023 is incorrect:
 The noise of the resistors does not sum, since the resistors are in parallel and load each other. It would be equal to a single 50 kΩ resistor producing 4.0 μV.
 The 113.1 value is output noise. The resistor noise needs to be multiplied by the gain to get the output noise, too.

0.1 F
Should be 0.1 μF

0.1 F
Should be 0.1 μF

The noise calculations have many errors. See annotations on https://via.hypothes.is/http://web.mit.edu/6.101/www/reference/op_amps_everyone.pdf for details

which is 100
actually should be multiplied by the noninverting noise gain, which is 101

TLE2201
Should be TLC2201


intranet.ee.ic.ac.uk intranet.ee.ic.ac.uk

The noise calculations have many errors. See annotations on https://via.hypothes.is/http://web.mit.edu/6.101/www/reference/op_amps_everyone.pdf for details

 Mar 2018

www.analog.com www.analog.comMT2042

The poles of the Bessel filter can be determined by locating all of the poles on a circle and separating their imaginary parts byn2where nis the number of poles.
This is incorrect:
 The poles are not located on a circle
 The imaginary parts of the poles are not equally spaced
To generate the poles of a Bessel filter you need to use rootfinding methods on the reverse Bessel polynomials. There's no other shortcut that I'm aware of.

The step response shows no overshoot
This is incorrect: There is a small amount of overshoot in Bessel filters.


www.radioelectronics.com www.radioelectronics.com

with no overshoot
This isn't quite correct: Bessel filters have a small amount of overshoot.
