56. One condition for positive feedback is that the phase shift around the feedback loop must be ________°.
(a) 0
(b) 90
(c) 180
(d) 45
57. The twin-T oscillator produces a ________ response.
(a) low-pass
(b) high-pass
(c) band-pass
(d) band-stop
58. The attenuation of the three-section RC feedback phase-shift oscillator is ________.
(a) 1/9.
(b) 1/30.
(c) 1/3.
(d) 1/29.
59. The feedback signal in a(n) ________ oscillator is derived from an inductive voltage divider in the LC circuit.
(a) Hartley
(b) Armstrong
(c) Colpitts
(d) Any of these
60. What is the ratio of the input impedance with series feedback to that without feedback?
(a) 1 + βA
(b) βA
(c) β
(d) 1
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