Consider a radio tuning circuit consisting of a 05 H inducto

Consider a radio tuning circuit consisting of a 0.5 H inductor connected in parallel with a Si p-n junction varicap diode (LC tank). The varicap diode has the following parameters: NA = 2×1015 cm-3, ND = 5×1016 cm-3, junction area = 0.15 mm2. The tuning circuit should be able to tune into any station within the commercial FM radio band from 88 MHz – 108 MHz. Find the range of the reverse bias voltage required to be applied across the varicap diode for the tuner to operate in this entire FM range.

Solution

1 • A coil in an ac generator rotates at 60 Hz. How much time elapses between successive peak emf values of the coil? Determine the Concept Successive peaks are one-half period apart. Hence the elapsed time between the peaks is ( ) ms .338 s 602 1 2 1 2 1 1- === f T . 2 • If the rms voltage in an ac circuit is doubled, the peak voltage is (a) doubled, (b) halved, (c) increased by a factor of 2 , (d) not changed. Picture the Problem We can use the relationship between V and Vpeak to decide the effect of doubling the rms voltage on the peak voltage. Express the initial rms voltage in terms of the peak voltage: 2 peak rms V V = Express the doubled rms voltage in terms of the new peak voltage : V\'peak 2 2 peak rms V\' V = Divide the second of these equations by the first and simplify to obtain: 2 2 2 peak peak rms rms V V\' V V = peak peak 2 V V\' = Solving for yields: V\'peak peak = 2VV\' peak a)( is correct. 3 • [SSM] If the frequency in the circuit shown in Figure 29-27 is doubled, the inductance of the inductor will (a) double, (b) not change, (c) halve, (d) quadruple. Determine the Concept The inductance of an inductor is determined by the details of its construction and is independent of the frequency of the circuit. The inductive reactance, on the other hand, is frequency dependent. b)( is correct. 4 • If the frequency in the circuit shown in Figure 29-27 is doubled, the inductive reactance of the inductor will (a) double, (b) not change, (