[TenTec] Sidetone revisited

[Dr. Gerald N. Johnson, electrical engineer]

The filtered sawtooth will always have the least delay. The filter can
be a simple two or three pole low pass. The effect of the twin T is to
make a narrow bandpass filter and its high Q in the feedback position of
an op amp makes its output slow to change.

If there's lots of signal from the sawtooth, a simple RC filter which
looses amplitude rapidly with the increasing stages can clean the
sawtooth adequately. No need for high Q components from either inductors
or the feedback of an op amp.

73, Jerry, K0CQ
-- 
Entire content copyright Dr. Gerald N. Johnson. Reproduction by
permission only.