Tag: electronic devices

Quizzes (9) Questions (113)

Questions Related to electronic devices

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

In a silicon transistor, the base  current is changed by 20 change of 0.02V in base to emitter voltage and a change of 2mA in the collector current.
(a) Find the input  resistance ${ \beta  } _{ ac }$ 
(b) If this transistor is used as an-amplifier. Find the voltage gain of the-amplifier with the load resistance 5k amplifier.

  1. a)100b)-500

  2. a)1000b)-500

  3. a)2000b)-5000

  4. a)10b)-5
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

(a) $n=\frac { { \triangle v } _{ BE } }{ { \triangle | } _{ B } } =\frac { 0.02 }{ 20\times { 10 }^{ -6 } } =1k\Omega $
${ \beta  } _{ ac }=\frac { { \triangle | } _{ c } }{ { \triangle | } _{ B } } =\frac { 2\times { 10 }^{ -3 } }{ 20\times { 10 }^{ -6 } } =100$
(b) Voltage gain,${ A } _{ v }=-{ g } _{ m }{ R } _{ L }=-\left( 0.1 \right) \left( 5\times { 10 }^{ 3 } \right) =-500$. $\left( since\quad { g } _{ m }={ \beta  } _{ ac }/n \right) $

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

The ac current gain of a transistor is $120$. What is the change in the collector current in the transistor whose base current changes by $100\ \mu A$?

  1. $6\ mA$
  2. $12\ mA$
  3. $3\ mA$
  4. $24\ mA$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given that,

Current gain$\beta =120\,A$

Base current $\Delta {{I} _{b}}=100\,\mu A$


We know that,

  $ {{\beta } _{ac}}=\dfrac{\Delta {{I} _{C}}}{\Delta {{I} _{B}}} $

 $ \Delta {{I} _{C}}=120\times 100\times {{10}^{-6}} $

 $ \Delta {{I} _{C}}=12\times {{10}^{-3}}\,A $

 $ \Delta {{I} _{C}}=12\,mA $

Hence, the collector current in the transistor is $12\ mA$

 

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

For a CE transistor amplifier, the audio signal voltage across the collector resistance of $2k\Omega $ is 2 V.Suppose the current amplification factor of the transistor is 100. The value of ${R _B}$ in series with ${V _{BB}}$ the supply of 2V, if the DC base current has to be 10 times the signal current is 

  1. $4k\Omega $
  2. $14k\Omega $
  3. $28k\Omega $
  4. $54k\Omega $
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

When a collector to emitter voltage is constant in a transistor, the collector current changes by $8.2mA$ when the emitter current changes by $8.3mA$. The value of forward current ratio $B$ is

  1. $82$
  2. $83$
  3. $8.2$
  4. $8.3$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The current gain beta is defined as delta_Ic / delta_Ib. Since delta_Ie = delta_Ic + delta_Ib, delta_Ib = delta_Ie - delta_Ic = 8.3mA - 8.2mA = 0.1mA. Thus, beta = 8.2mA / 0.1mA = 82.

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

In the CB mode of a transistor when the collector voltage is changed by $0.5V$. The collector current changes by $0.05mA$. The output resistance will be

  1. $10k\Omega$
  2. $20k\Omega$
  3. $5k\Omega$
  4. $2.5k\Omega$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Output resistance r_o = delta_Vcb / delta_Ic = 0.5V / 0.05mA = 0.5 / 0.00005 = 10,000 Ohms = 10k Ohm.

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

Consider an n-p-n transistor amplifier in common-emitter configuration. The current gain of the transistor is $100$. if the collector current changes by $1mA$. What will be the change in emitter current.

  1. $1.1mA$
  2. $1.01mA$
  3. $0.01mA$
  4. $10mA$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given beta = 100, delta_Ic = 1mA. Since beta = delta_Ic / delta_Ib, delta_Ib = 1mA / 100 = 0.01mA. Then delta_Ie = delta_Ic + delta_Ib = 1mA + 0.01mA = 1.01mA.

Multiple choice transistor and its types the bipolar junction transistor electronic devices semiconductor electronics: materials, devices and simple circuits physics

Power gain for $N - P - N$ transistor is $10^6$, input resistance $100 \Omega$ and output resistance $1000 \,\Omega$. find out current gain.

  1. $100$
  2. $150$
  3. $200$
  4. $50$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Power gain = $(Current \, gain)^2 \left(\dfrac{R _{out}}{R _{in}} \right)$
$10^6 = \beta^2 \times \dfrac{10^4}{100}$
$\beta = 100$