This set of VLSI Multiple Choice Questions & Answers (MCQs) focuses on “BiCMOS Logic Gates”.
1. The BiCMOS are preferred over CMOS due to:
a) Switching speed is more compared to CMOS
b) Sensitivity is less with respect to load capacitance
c) High current drive capability
d) All of the mentioned
Explanation: These are the 3 advantages of BiCMOS over CMOS.
2. The transistors used in BiCMOS are:
c) Both BJT and MOSFETs
Explanation: BiCMOS is a combination of both MOSFET and BJT.
3. The high current driving capability of the BiCMOS is due to:
a) NMOS in saturation mode
b) PMOS in saturation mode
Explanation: BJT has the high current driving capability.
4. In BiCMOS inverter, the BJT used are:
a) Only Npn BJT
b) Only Pnp BJT
c) Both npn and pnp BJT
d) Multi emitter npn BJT
Explanation: npn BJTs are used in BiCMOS inverter.
5. The drawback of the BiCMOS circuits are:
a) Sensitivity is less load capacitance
b) Bipolar transistors are used for driving current to the load capacitance but not for the logic operations
c) Increased fabrication Complexity
d) All of the mentioned
Explanation: The other 2 are the merits of BiCMOS, Increased fabrication Complexity is a demerit of BiCMOS circuits.
6. The Bipolar Transistor is fabricated on :
a) Same substrate of nMOS
b) N-well in p Substrate
c) P-well in n Substrate
d) Same substrate of pMOS
Explanation: BiCMOS is fabricated on the same substrate of nMOS.
7. The n-well created for Bipolar Transistor in BiCMOS is used as:
d) None of the mentioned
Explanation: The created nWell is used as Collector region for BiCMOS.
8. The n-well collector is formed by:
a) Lightly doped n-type epitaxial layer on p-Substrate
b) Heavily doped n-type epitaxial layer on p-Substrate
c) Lightly doped n-type diffused layer on p-Substrate
d) Heavily doped n-type diffused layer on p-Substrate
Explanation: To make the doping concentration less than the emitter.
9. The collector contact region is doped with higher concentration of n-type impurities due to:
a) It creates a depletion region at the contact surface
b) It creates a low conductivity path between collector region and contact
c) It reduces a contact resistance
d) It can withstand high voltages as compared to collector region
Explanation: The collector contact region is doped with higher concentration of n-type impurities reduces contact resistance.
In the above diagram of BiCMOS, the labels a,b,c,d denote:
a) A = Collector, B = Base, C = Source, D = Drain
b) A = Emitter, B = Base, C = Drain, D = Source
c) A = Emitter, B = Collector, C = Source, D = Drain
d) A = Collector, B = Emitter , C = Drain, D = Source
12. The BJT in BiCMOS works as a:
a) Current controlled Voltage source
b) Voltage controlled Current source
c) Current controlled current source
d) Voltage controlled current source
Explanation: The Current Ic and Ie are controlled by base emitter bias voltage.
13. In BiCMOS, the analysis of the operation of BJT is well explained by:
a) RC Model
b) Emitter resister model
c) Ebers Moll Model
d) Hybrid model
Sanfoundry Global Education & Learning Series – VLSI.
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