1 What type of sine-wave oscillator uses a tapped inductor to provide the positive feedback required for oscillation?
(a) Clap (b) Colpitts (c) Hartley (d) Pierce. 2 What type of capacitor is usually used in the tuned circuits of oscillators? (a) electrolytic (b) low loss (c) high voltage (d) surface mount. 3. An LC oscillator uses a 100 H inductor. What value of capacitor is required to tune it to 1.8 MHz? (a) 16 pF (b) 22 pF (c) 47 pF (d) 78 pF. 4 An RC phase-shift oscillator uses three identical RC stages in the feedback circuit. What phase shift is required in each stage? (a) 30 (b) 60 (c) 90 (d) 120. 5 A timebase circuit uses a Miller integrator to produce the sweep signal for an oscilloscope. If the timebase circuit uses a bipolar junction transistor (BJT), where is the integrator capacitor connected? (a) collector-emitter (b) base-emitter (c) collector-base (d) base-positive supply 6. The conditions for oscillation to occur are described by which of the following? (a) Nyquist therem (b) thearkhausen criterion (c)Faradays law (d)Lenz law
7. A thermister can be used to stabilise the gain of simple oscillators. (a)True (b)false 8. What elements are found within the equivalent circuit of a crystal? (a) Resistance alone. (b) Resistance and capacitance. (c) Resistance and inductance. (d) Resistance, capacitance and inductance 9. In order to ensure stability in a circuit, the designer must ensure that the phase shift reaches 180 degrees before the gain falls to unity. (a)True (b)false 10.What is the name given to the amount (in dB) by which the loop gain is less than 0 dB when the phase reaches 180 degrees? (a)The phase margin. (b)The transition point. (c) The zero-gain bandwidth. (d) The gain margin. 11. Frequency of oscillation of a Wein bridge oscillator is given by 1/6RC 1/2RC 2RC 1/RC
12.Which of the following is not true? An oscillator is circuit that converts dc to ac. An oscillator is an amplifier that supplies it own input signal. All oscillators generate sine wave. In-phase feedback is called positive feedback. 13. What do phase-shift oscillators, twin-T oscillators and Wein-bridge oscillators have in common? They use RC frequency control They have a sinusoidal output They use amplifier gain to overcome feedback loss All of the above 14. The stability of frequency of oscillation is high if:
15. The primary advantage of a crystal oscillator is that: It can oscillate at any frequency It gives a high output voltage Its frequency of oscillation remains almost constant It operates on a very low dc supply voltage
16. A Hartley oscillator circuit uses: (a) A tapped inductor (b) A tapped capacitor (c) Both (a) and (b) (d) A tapped inductor for inductive feedback 17. A Colpitts oscillator uses: A tapped inductor A tapped capacitor Both the above None of the above 18. An oscillator circuit using a quartz crystal has: High-frequency stability Low-frequency stability Medium-frequency stability None of the above 19.In a feedback oscillator, constant amplitude oscillation are obtained when loop gain A equals: 0 -1 1 20. Crystal oscillator uses: Silicon crystal Germanium crystal Crystal diode Piezo-electric quartz crystal
21. Barkhausen criterion for sustained oscillation gives: A = 1 A = 0 A= A = 1/ 22. Quartz crystal oscillators are popularly used because of: High Q and high frequency stability Low Q and high frequency stability Low Q and large output power High Q and large output power 23. The crystal oscillator frequency is highly stable due to: Crystal structure High Q of the crystal Vibration of the crystal Rigidity of the crystal 24. The most likely application of a crystal oscillator is: As an RF test oscillator As an electronic organ for home As a hi-fi test audio-frequency sweep generator In commercial radio transmitter
25. In RC phase-shift oscillator using FET and 3-section RC phase-shift network, the condition for sustained oscillation is
>6 > 29 > 4n + 23 + 29/n, n = Rd/R > 23 + 29/n 26. FET RC phase-shift oscillator has angular frequency of oscillation equal to: (where, R and C refer to each section of three section RC phase-shift network.) 1/3RC 1/6RC
27. In FET Hartley oscillator, frequency of oscillation is: (where, 0 is frequency of resonance.) 0 << 0 >> 0 0 (L1/L2) 28. The feedback factor at frequency of oscillation of Wein-bridge oscillator is: 1/3 3 1/29 -1/29
29. The minimum number of RC sections required in phase-shift oscillator are: Two Three Four None
30. Wein-bridge oscillator is most often used whenever: Wide range of high purity sine waves is to be generated High feedback ratio is needed Square output waves are required Extremely high resonant frequencies are required
