Electronic Circuits I Set 2

Electrical Engineering

Practice Mode Previous Next
On This Page

This set of Electronic Circuits 1 Multiple Choice Questions & Answers (MCQs) focuses on Electronic Circuits I Set 2

Q1 | From the given circuit, using silicon BJT, what is the value of the saturation collector current?
  • 5 ma
  • 5.36 ma
  • 5.45 ma
  • 10.9 ma
Answer: 5.36 ma
Explaination:
to obtain an approximate answer, under saturation the bjt is on and hence acts like a short circuit. however, ideally a drop exists for the transistor which is a fixed value. for an exact answer, if the bjt is a silicon transistor, then drop vce = 0.2v and current is 12-0.2/2.2=5.36 ma.
Q2 | In the given circuit, what is the value of IC if the BJT is made of Silicon?
  • 2.01 ma
  • 2.01 ua c) 10.05 ma d) 10.05 ua
Answer: 2.01 ma
Explaination:
consider the bjt to be in saturation. then ic=20-0.2/2k=9.9 ma and ib=20-0.8/430k=0.044 ma
Q3 | In the given circuit, using a silicon BJT, what is the value of VCE?
  • 20 v
  • 15.52 v
  • 14.98 v
  • 13.97 v
Answer: 15.52 v
Explaination:
consider the bjt to be in saturation. then ic=20-0.2/2k=9.9 ma and ib=20-0.8/430k=0.044 ma
Q4 | In the given circuit, what is the value of VE when using a silicon BJT?
  • 2.01 v
  • 0.28 v
  • 0 v
  • 2.28 v
Answer: 2.28 v
Explaination:
consider the bjt to be in saturation. then ic=20-0.2/2k=9.9 ma and ib=20-0.8/430k=0.044 ma
Q5 | In the given circuit using a silicon BJT, what is the value of saturation collector current?
  • 10 ma
  • 8.77 ma
  • 6.67 ma
  • 5 ma
Answer: 6.67 ma
Explaination:
to obtain an approximate answer, under saturation the bjt is on and hence acts like a short circuit. however, ideally a drop exists for the transistor which is a fixed value. for an exact answer, if the bjt is a silicon transistor, then drop vce = 0.2v and current is 20-0.2/2.2=9.9 ma.
Q6 | What is Stability factor?
  • ratio of change in collector current to change in a current amplification factor
  • ratio of change in collector current to change in base current
  • current amplification factor
  • ratio of base current to collector current
Answer: ratio of change in collector current to change in a current amplification factor
Explaination:
stability factor is defined as the rate at which collector current changes when base to emitter voltage changes, keeping base
Q7 | The base current for a BJT remains constant at 5mA, the collector current changes from 0.2mA to 0.3 mA and beta was changed from 100 to 110, then calculate the value of S.
  • 0.01m
  • 1m
  • 100m
  • 25m
Answer: 0.01m
Explaination:
since the current in the above case, remains constant, therefore stability factor is 0.01 as it is defined as the ratio of change in collector current to change in beta. s=change in collector current/change in beta=0.1ma/10=0.01m.
Q8 | For a n-p-n transistor, the collector current changed from 0.2mA to 0.22mA resulting a change of base emitter voltage from 0.8v to 0.8005V. What is the value of Stability factor?
  • 0
  • 0.25
  • 0.04
  • 0.333
Answer: 0.04
Explaination:
change in vbe = 0.0005v change in collector current = 0.02ma
Q9 | There are two transistors A and B having ‘S’ as 25 and 250 respectively, on comparing the value of S, we can say B is more stable than A.
  • true
  • false
Answer: false
Explaination:
more the value of s, lesser the stability, since a has lesser s value the
Q10 | For a fixed bias circuit having Ic = 0.3mA and In=0.0003mA, S is                             
  • 100
  • 0
  • 11 d) 111
Answer: 11 d) 111
Explaination:
for fixed bias s=1+beta beta=ic/ib=10
Q11 | For a fixed bias circuit having RC=2Kohm and VCC=60V, IB=0.25mA and S=101, find Vce.
  • 12v
  • 10v
  • 5v
  • 2.5v
Answer: 10v
Explaination:
s = 1 + beta,
Q12 | For an ideal transistor having a fixed bias configuration, what will be the value of Beta?
  • 0
  • 2
  • -1
  • 1
Answer: -1
Explaination:
s = 1 + beta s = 0
Q13 | The temperature changes do not affect the Stability.
  • true
  • false
Answer: false
Explaination:
the temperature changes the value of beta which in turn changes the stability of the transition. the temperature changes affect the mobility of the charge carries which results in a change of the current parameters affecting stability.
Q14 | Comparing fixed and collector to base bias which of the following statement is true?
  • fixed bias is more stable
  • collector to base bias is more stable
  • both are the same in terms of stability
  • depends on the design
Answer: collector to base bias is more stable
Explaination:
for fixed bias circuit, s = 1+beta, more the beta, lesser the stability for collector to base bias s = (1+beta)/(1+beta(rc/rc+rb))
Q15 | The compensation techniques are used to                   
  • increase stability
  • increase the voltage gain
  • improve negative feedback
  • decrease voltage gain
Answer: increase the voltage gain
Explaination:
usually, the negative feedback is used to produce a stable operating point.
Q16 | Compensation techniques refer to the use of                   
  • diodes
  • capacitors
  • resistors
  • transformers
Answer: diodes
Explaination:
compensation techniques refer to the use of temperature sensitive devices such as thermistors, diodes, transistors, sensistors etc to compensate variation in currents. sometimes for excellent bias and thermal stabilization, both stabilization and compensation techniques are used.
Q17 | In a silicon transistor, which of the following change significantly to the change in IC?
  • vce
  • ib
  • vbe
  • b) ie
Answer: vbe
Explaination:
for germanium transistor, changes in ico with temperature contribute more serious problem than for silicon transistor. on the other hand, in a silicon transistor, the changes of vbe with
Q18 | What is the compensation element used for variation in VBE and ICO?
  • diodes
  • capacitors
  • resistors
  • transformers
Answer: diodes
Explaination:
a diode is used as the compensation element used variation in vbe and ico. the diode used is of the same material and type as that of transistor. hence, the voltage across the diode has same temperature coefficient as vbe of the transistor.
Q19 | The expression for IC in the compensation for instability due to ICO variation                   
  • βi+βio+βico
  • βi+βio
  • βio+βico
  • βi+βico
Answer: βi+βio+βico
Explaination:
in this method, diode is used for the compensation in variation of ico. the diode used is of the same material and type as that of transistor. hence, the reverse saturation current io of the diode will increase with temperature at the same rate as the transistor collector saturation current ico.
Q20 | Which of the following has a negative temperature coefficient of resistance?
  • sensistor
  • diode
  • thermistor
  • capacitor
Answer: thermistor
Explaination:
the thermistor has a negative temperature coefficient of resistance. it
Q21 | Which of the following has a negative temperature coefficient of resistance?
  • capacitor
  • diode
  • thermistor
  • sensistor
Answer: sensistor
Explaination:
the sensistor has a positive temperature coefficient of resistance. it is a temperature sensitive resistor. it is a heavily doped semiconductor. when voltage is decreased, the net forward emitter voltage decreases. as a result the collector current decreases.
Q22 | Increase in collector emitter voltage from 5V to 8V causes increase in collector current from 5mA to 5.3mA. Determine the dynamic output resistance.
  • 20kΩ
  • 10kΩ
  • 50kΩ
  • 60kΩ
Answer: 10kΩ
Explaination:
ro=∆vce/∆ic
Q23 | The output resistance of CB transistor is given by                    
  • ∆vcb/∆ic
  • ∆vbe/∆ib
  • ∆vbe/∆ic
  • ∆veb/∆ie
Answer: ∆vcb/∆ic
Explaination:
the ratio of change in collector base voltage (∆vcb) to resulting change in collector current (∆ic) at constant emitter current (ie) is defined as output resistance.
Q24 | The negative sign in the formula of amplification factor indicates                   
  • that ie flows into transistor while ic flows out it
  • that ic flows into transistor while ie flows out it
  • that ib flows into transistor while ic flows out it
  • that ic flows into transistor while ib flows out it
Answer: that ie flows into transistor while ic flows out it
Explaination:
when no signal is applied, the ratio of collector current to emitter current is called dc alpha, αdc of a transistor. αdc=- ic/ie. it is the measure of the quality of a transistor. higher is the value of α, better is the transistor in the sense that collector current approaches the emitter current.
Q25 | In the given situation for n-channel JFET, we get drain-to-source current is 5mA. What is the current when VGS = – 6V?
  • 5 ma
  • 0.5a
  • 0.125 a
  • 0.5a
Answer: 0.125 a
Explaination:
ids = idss(1-vgs/vp)2 when vgs = 0, idss = ids = 5ma when vgs = -6v, ids = 5ma(1 + 4)2 ids = 5 x 25 = 125 ma.
Previous Next