# VLSI Questions and Answers – Transconductance and Voltage Swing

This set of Basic VLSI Questions and Answers focuses on “Transconductance and Voltage Swing”.

1. Gain of MESFET is _______ to transconductance.
a) directly proportional
b) indirectly proportional
c) exponentially dependent
d) does not depend on

Explanation: The gain of the MESFET is directly dependent on the transconductance and output conductance of the device.

2. Transconductance gives the relationship of
a) Ids and Vds
b) Vds and Vgs
c) Ids and Vgs
d) Ids and d

Explanation: Transconductance describes the relationship between the output current Ids and the input control voltage Vgs.

3. Output conductance gives the slope of linear characteristics.
a) true
b) false

Explanation: Output conductance is also used to measure the gain of MESFET and it gives the slope of output characteristics.

4. The transconductance value in cut off region is
a) Vds
b) 1
c) cannot be determined
d) 0

Explanation: The transconductance value for cut off region is 0 and it is the relationship between Ids and Vgs.

5. GaAs device has
a) high bandwidth
b) high transconductance
c) low gate capacitance
d) all of the mentioned

Explanation: GaAs devices have high transconductance, very low gate capacitance, high gain and high bandwidth.

6. Transconductance is not influenced by transistor size.
a) true
b) false

Explanation: Transconductance is independent of process and slightly influenced by the transistor size. In GaAs transconductance is both process and size dependent.

7. Switching speed does not depend on
a) gate length
b) gate voltage
c) carrier mobility
d) doping level

Explanation: The switching speed of the device depends on gate length, gate voltage and carrier mobility in the channel but does not depend on the doping level.

8. The output conductance value in cut off region is
a) Vds
b) 1
c) cannot be determined
d) 0

Explanation: The output conductance value for cut off region is 0. This gives the slope of output characteristics.

9. To improve the switching speed
a) voltage swing should be increased
b) voltage swing should be decreased
c) gate length should be increased
d) gate thickness should be increased

Explanation: To improve the switching speed, the logic voltage swing should be increased and the gate length should be reduced. The increase in switching speed results in an increase in dissipation.

10. The device turns off when
a) Vlow > Vt
b) Vlow < Vt
c) Vhigh < Vt
d) Vhigh > Vt

Explanation: To establish the logic voltage swing and to turn off the device, Vlow the low logic voltage level must be less than the threshold voltage Vt.

11. For finding transconductance which is kept as constant?
a) Vss
b) Vdd
c) Vds
d) Vgs

Explanation: For finding transconductance, Vds is kept as constant and the ratio of the variation or change in Ids and Vgs is obtained.

12. Transconductance value is same in linear and saturation region.
a) true
b) false

Explanation: Transconductance value is same in case of linear and saturation region whereas it is 0 in cut-off region.

13. In bipolar transistor, transconductance is _______ to collector current.
a) directly related
b) inversely related
c) exponentially related
d) not related

Explanation: In bipolar transistor, transconductance is directly proportional to the collector current. It is given as gm = Ic(q/kT).

14. Figure of merit does not depend on saturation velocity.
a) true
b) false

Explanation: Figure of merit is directly related to saturation velocity Vsat. It can be given as ft = Vsat/2(pi*L).

Sanfoundry Global Education & Learning Series – VLSI.

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