GC_ET_PFB-rg.html

2018-01-10

11:08:01

Based on circuit design by Dr. Josef Punchochar

Associate Professor

VŠB-Technical University of Ostrava, Ostrava · Department of Electrical Engineering

Copy from Josef Punchochar article :

Developed into this by Glen Ellis :
Example of circuit modification to handle Positive Boot-Strap Feedback via Multiple-Feedback Band Pass Filter.
Advantage is : Adjust f(0) via a single resistor R(freqAdj) +/- 300 Hz.

SPICE circuit, 161210, Glen Ellis.
Based on circuit design by Josef Punchochar, Research Gate Net
Example of circuit modification to handle Positive Boot-Strap Feedback via Multiple-Feedback Band Pass Filter.
Advantage : Adjust f(0) via a single resistor R(freqAdj) +/- 300 Hz.

Balance between Positive & Negative FB
Too much FeedBack will transform circuit into a Notch Filter.

V(out) is NetVout
f(0) = 700 Hz
FeedBack Q=2
Effecive Q=7
BW=100 Hz

Original NetSigIn ( source signal ) is flat ( green ).
FeedBack inverted ( black ) (generated at Q=2)
Overall Response is Q=7 Positive BandPass ( blue ).

Transient Plot

Adjust f(0) via a Single Resistor R(freqAdj) +/- 300 Hz.
Change f(0) via R6 .
Initially R(freq) is 6500 Ohm. Adjust : Up = lower f(0) and Down = higher f(0).

In f(0) change,
Gain will change as the minor ratio of R(in) / R(freq).
Q will change as squareroot of delta(f) change.
But BW will remain same.
( Author uses this method for adjusting f(0) change of +/- 300 Hz. )

*** Demonstrating shifting f(0) via R(freqAdj)

*** Demonstrating circuit to generate bode of shifting f(0) via R(freqAdj)

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