Unit 4: Amplifiers and Oscillators - Practice Quiz

1 In an RC coupled amplifier, the coupling between two stages is provided by a:

2 The gain of an RC coupled amplifier falls at low frequencies mainly due to the:

3 The gain of an RC coupled amplifier falls at high frequencies mainly due to:

4 The frequency response curve of an RC coupled amplifier is flat over the:

5 The bandwidth of an amplifier is defined as the difference between the:

6 At the cutoff frequencies, the voltage gain of an amplifier falls to what fraction of its maximum value?

7 In negative feedback, the feedback signal is:

8 Positive feedback is mainly used in:

9 In a feedback amplifier, the fraction of output fed back to the input is denoted by the symbol:

10 The gain of an amplifier with negative feedback is given by:

11 Negative feedback in an amplifier causes the gain to:

12 Negative feedback affects the bandwidth of an amplifier by:

13 Voltage-series negative feedback affects the input impedance by:

14 One of the main advantages of negative feedback is:

15 According to the Barkhausen criterion, the loop gain of an oscillator for sustained oscillation must be:

16 For sustained oscillations, the total phase shift around the feedback loop must be:

17 An RC phase shift oscillator using three RC sections produces a total phase shift of:

18 The RC phase shift oscillator is generally used to generate:

19 The frequency-determining tank circuit of a Hartley oscillator consists of:

20 The tank circuit of a Colpitts oscillator consists of:

21 In a single stage RC coupled CE amplifier, the gain falls at low frequencies primarily because of the:

22 The gain of an RC coupled CE amplifier falls at high frequencies mainly due to:

23 If the lower and upper cut-off frequencies of an RC coupled amplifier are and , the bandwidth is approximately:

24 At the half-power (cut-off) frequencies of an amplifier, the voltage gain drops to what fraction of its mid-band value?

25 In a feedback amplifier, the feedback is termed negative (degenerative) when the feedback signal is:

26 The general expression for the gain of a negative feedback amplifier is:

27 An amplifier has an open-loop gain of and uses negative feedback with . The closed-loop gain is:

28 When negative feedback with loop gain is applied, the bandwidth of the amplifier is:

29 In a voltage-series (series-shunt) negative feedback amplifier, the input and output impedances respectively:

30 The main advantage of negative feedback regarding noise generated within the amplifier is that it:

31 An amplifier with gain has a gain variation of . With negative feedback giving , the gain variation reduces to approximately:

32 According to the Barkhausen criterion, sustained oscillations occur when the loop gain and total phase shift are:

33 For an oscillator to start up reliably, the loop gain at the instant of switch-on should be:

34 In an RC phase shift oscillator using three identical RC sections, each section must provide a phase shift of:

35 The frequency of oscillation of a transistor RC phase shift oscillator with three equal RC sections is given by:

36 In a Hartley oscillator, the frequency of oscillation depends on a capacitor and:

37 A Hartley oscillator has , (no mutual coupling) and . The frequency of oscillation is approximately:

38 In a Colpitts oscillator the tank circuit consists of two capacitors , and one inductor . The oscillation frequency uses the capacitance:

39 A Colpitts oscillator has , and . The frequency of oscillation is approximately:

40 In a Wien bridge oscillator with equal components (, ), the frequency of oscillation is:

41 In a single-stage RC coupled CE amplifier, the lower cutoff frequency contributed by the coupling capacitor at the output is given by . If , and , what is the approximate lower cutoff frequency?

42 At high frequencies in an RC coupled CE amplifier, the gain falls primarily due to which effect?

43 The mid-band gain of an RC coupled CE amplifier is and its bandwidth is . If a second identical stage is cascaded, the overall bandwidth (assuming identical non-interacting stages, shrinkage factor for ) becomes approximately:

44 In the hybrid- model, the Miller input capacitance at the base is . For , and , the effective input capacitance is:

45 An amplifier has open-loop gain (negative sign indicating phase shift). A feedback network with (also inverting) is applied. What kind of feedback results and what is the closed-loop gain magnitude?

46 For positive feedback, the loop gain condition that leads to sustained instability (oscillation onset) requires:

47 A voltage-series (series-shunt) negative feedback amplifier has open-loop gain , input impedance and . What is the closed-loop input impedance?

48 A voltage-shunt (shunt-shunt) feedback amplifier reduces output impedance. If , , , the closed-loop output impedance is:

49 An amplifier with gain and bandwidth is given negative feedback with . Assuming constant gain-bandwidth product, the new bandwidth is:

50 The desensitivity factor of a negative feedback amplifier reduces gain sensitivity. If changes by and , the fractional change in closed-loop gain is approximately:

51 The Barkhausen criterion states two conditions for sustained oscillation. Which statement most accurately describes the practical startup requirement?

52 In an RC phase shift oscillator using a BJT with three RC sections, the frequency of oscillation is where . For minimum effect (), . With , , the frequency is approximately:

53 For a transistor RC phase shift oscillator to sustain oscillations, the minimum voltage gain required from the amplifier stage is:

54 A Hartley oscillator has , (with mutual inductance ) and . The frequency of oscillation is approximately:

55 In a Hartley oscillator, the condition for sustained oscillation relates the transconductance/gain to the inductor ratio. The gain requirement is approximately (or depending on tap). What primarily determines the feedback fraction ?

56 A Colpitts oscillator has , and . The oscillation frequency is approximately:

57 In a Colpitts oscillator, the minimum gain condition for sustained oscillation is . If and , the minimum voltage gain required is:

58 A Wien bridge oscillator uses and in both arms of the frequency-selective network. The oscillation frequency and required minimum amplifier gain are:

59 In a Wien bridge oscillator, if the non-inverting amplifier gain is set exactly at , a practical problem arises. What is it and the common remedy?

60 A negative resistance oscillator (e.g., using a tunnel diode) sustains oscillations when the device's negative resistance cancels the tank's positive loss resistance . For a tank with , and series loss , the oscillation frequency is approximately: