Electronic Devices and Circuits 3rd. Edition by S. Salivahanan, N Suresh Kumar | 9781259006418 | 1259006417 | Holooly

Electronic Devices and Circuits [EXP-37060]

340 SOLVED PROBLEMS

Question: 11.3

(a) A multistage amplifier employs five stages each of which has a power gain of 30. What is the total gain of the amplifier in dB? (b) If a negative feedback of 20 dB is employed, find the resultant gain.

Verified Answer:

Given, the gain of each stage = 30 and number of s...

Question: 4.11

(a) The resistivities of the P-region and N-region of a germanium diode are 6 Ω-cm and 4Ω-cm, respectively. Calculate the contact potential Vo and potential energy barrier Eo. (b) If the doping densities of both P and N-regions are doubled, determine Vo and Eo. Given that q = 1.602 × 10^–19 C,

Verified Answer:

(a) Resistivity,

\rho =...

Question: 13.3

A 1 mH coil with Q = 100 is used in a tuned amplifier. The transistor has β = 100 and ro = 100 kΩ and input resistance Ri = RB || rπ = 10 kΩ. (a) Determine the value of tuning capacitance (C) such that the amplifier has a maximum gain at fo = 50 kHz. Also calculate the value of this gain for the

Verified Answer:

The small-signal model of the amplifier whose outp...

Question: 18.16

A 230 V, 50 Hz voltage is applied to the primary of a 4:1step-down transformer used in a bridge rectifier having a load resistance of 600 Ω. Assuming the diodes to be ideal, determine (a) d.c. output voltage, (b) d.c. power delivered to the load, (c) PIV, and (d) output frequency.

Verified Answer:

(a) The rms value of the transformer secondary vol...

Question: 18.10

A 230 V, 60 Hz voltage is applied to the primary of a 5:1 step-down, center-tap transformer use in a full wave rectifier having a load of 900 Ω. If the diode resistance and secondary coil resistance together has a resistance of 100 Ω, determine (a) d.c. voltage across the load,

Verified Answer:

The voltage across the two ends of secondary = [la...

Question: 18.35

A 24 V, 600 mW Zener diode is used for providing a 24 V stabilized supply to a variable load. If the input voltage is 32 V, calculate (i) the value of series resistance required and (ii) diode current when the load is 1200 Ω.

Verified Answer:

Given

V_{0}

= 24 V,

V_{i}[/l...

Question: 11.12

A BJT has gm = 38 mhos, rb’e = 5.9 kΩ, hie = 6 kΩ, rbb’ = 100Ω, Cb’c = 12 pF, Cb’e = 63 pF, and hfe = 224 at 1 kHz. Calculate α and β cut-off frequencies and fT.

Verified Answer:

f_{\alpha } \approx \frac{h_{fe}}{2\pi r_{b...

Question: 11.10

A BJT has hie = 6 kΩ and hfe = 224 at IC = 1 mA, with fT = 80 MHz and Cb’c = 12 pF. Determine (a) gm (b)rb’e (c) rbb’ and (d) cb’e at room temperature and a collector current of 1 mA. Determine the parameters, gm, rb’e rbb’ and Cb’e of the small signal high frequency model of the BJT.

Verified Answer:

g_{m}=\frac{I_{C}(mA)}{26 mV}=\frac{1}{26}...

Question: 11.15

A BJT transistor amplifier shown in Fig. 11.27 has RE = RC = 1 kΩ, RS = 600, RL = 2 k and transistor parameters as β = 100 and rπ = 1 kΩ. Determine the values of CC1, CC2 and CE needed to obtain fL = 50 Hz.

Verified Answer:

\omega _{1p} = 2 \pi f_{L} = 100 \pi rad...

Question: 18.18

A bridge rectifier uses four identical diodes having forward resistance of 5 Ω and the secondary voltage is 30 V(rms). Determine the d.c. output voltage for I d.c. = 200 mA and value of the output ripple voltage.

Verified Answer:

Given Transformer secondary resistance = 5 Ω Secon...

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