Questions Related to physics

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

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

In a common emitter transistor amplifier $\beta$ $= 60$, $R _0$ $= 5000$$\Omega$ and internal resistance of a transistor is $500$$\Omega$. The voltage amplification of amplifier will be

  1. $500$
  2. $460$
  3. $600$
  4. $560$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Voltage amplification, $\displaystyle A _v = \beta \dfrac{R _0}{R _i} = 60 \times \dfrac{5000}{500} = 600$

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

In a triode, $g$$ _m$ $= 2$ $\times$$ 10$$^{-3}$ $\Omega^{-1}$, $\mu$ $= 42$, resistance of load, $R = 50k\Omega$. The voltage amplification obtained from this triode will be

  1. $30.42$
  2. $29.57$
  3. $28.18$
  4. $27.15$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Voltage gain, $\displaystyle A _v = \beta \dfrac{R _L}{R _i} = 0.6 \times \dfrac{24}{3} = 4.8$

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

The grid voltage of any triode valve is changed from -1 volt to -3 volt and the mutual conductance is 3$\times$ 10$^{-4}$ mho. The change in plate circuit current will be

  1. 0.8 mA

  2. 0.6 mA

  3. 0.4 mA

  4. 1 mA

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$\displaystyle g _m = \frac{\Delta I _p}{\Delta V _g}$

or $\Delta I _p = g _m \times \Delta V _g = 3 \times 10^{-4} \times [-3-(-1)]$
$= - 0.6 \times 10^{-3} A$ = shortage of $0.6 \times 10^{-3}A$