Transconductance MCQ Quiz in मराठी - Objective Question with Answer for Transconductance - मोफत PDF डाउनलोड करा
Last updated on Apr 4, 2025
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Transconductance Question 1:
Two n channel MOSFETs are fabricated and biased in saturation region in such a way that the first one has width as well as VGS-VTH double as those of the second one. All other parameters remain the same. What is the ratio of drain currents of the transistors?
Answer (Detailed Solution Below)
Transconductance Question 1 Detailed Solution
- The drain current (ID) of a MOSFET in the saturation region is given by the equation:
ID = (1/2) × μn × Cox × (W/L) × (VGS - VTH)²,
where:- μn: Electron mobility
- Cox: Gate-oxide capacitance per unit area
- W: Width of the MOSFET channel
- L: Length of the MOSFET channel
- VGS: Gate-to-source voltage
- VTH: Threshold voltage
- All other parameters (μn, Cox, and L) are constant in this problem.
- Therefore, the drain current is directly proportional to both the width of the MOSFET (W) and the square of the overdrive voltage (VGS - VTH).
Solution:
Let the parameters of the second MOSFET (MOSFET 2) be:
- Width: W
- Overdrive voltage: (VGS - VTH)
- Drain current: ID2
For the first MOSFET (MOSFET 1), the parameters are:
- Width: 2W (double the width of MOSFET 2)
- Overdrive voltage: 2(VGS - VTH) (double the overdrive voltage of MOSFET 2)
- Drain current: ID1
The drain current for MOSFET 2 is:
ID2 = (1/2) × μn × Cox × (W/L) × (VGS - VTH)²
The drain current for MOSFET 1 is:
ID1 = (1/2) × μn × Cox × (2W/L) × [2(VGS - VTH)]²
Simplifying ID1:
ID1 = (1/2) × μn × Cox × (2W/L) × 4(VGS - VTH)²
ID1 = 4 × (1/2) × μn × Cox × (W/L) × (VGS - VTH)²
ID1 = 8 × ID2
Conclusion:
The ratio of the drain currents of the two MOSFETs is:
ID1 : ID2 = 8 : 1
The correct answer is Option 3.
Transconductance Question 2:
The small signal voltage gain of the common-source Amplifier shown in the figure if
Answer (Detailed Solution Below) -4 - -3
Transconductance Question 2 Detailed Solution
Concept:
Voltage gain is given by:
Av = - gmRD
Calculation:
AV = - gmRD
= -3.33
Transconductance Question 3:
The small signal output resistance R0 of the NMOS circuit if ID = 0.5 mA, λ = 0.02 V-1,
Answer (Detailed Solution Below) 2.1 - 2.3
Transconductance Question 3 Detailed Solution
The small signal model with a test voltage Vx is shown.
The output resistance is given by
From the circuit
Vgs = Vx
Applying KCL
Calculation of gm
= 0.447 mA/V
= 2.19 k
Transconductance Question 4:
The table shows the standard values of NMOS transistor using 0.25 μm technology.
|
Parameter |
Value |
|
tox (nm) |
6 |
|
Cox (bF/μm2) |
5.8 |
|
μ (cm2/V-sec) |
460 |
|
μ - Cox (μA/V2) |
267 |
|
Vto (V) |
0.5 |
|
VDD (V) |
2.5 |
|
VA’|(V/μm) |
5 |
|
C0V (bF/μm) |
0.3 |
If NMOS is operating at 100 μA of drawn current and L = 0.4 um W = 4 um. The intrinsic gain of the NMOS is
Answer (Detailed Solution Below)
Transconductance Question 4 Detailed Solution
For NMOS:
= 0.73 mA/V
A0 = gm r0 = 0.73 × 20
= 14.6 V/V
Transconductance Question 5:
Consider the CMOS common-source amplifier shown in the figure. If VDD = 3V, Vtn = |Vtp| = 0.6 V,
Answer (Detailed Solution Below)
Transconductance Question 5 Detailed Solution
The circuit shown is CMOS circuit implementation of the common-source amplifier.
Here load = Q2 transistor and output is taken across Q1
Av = -gm1 (r01||r02)
= - 0.63 (mA/V) × (200||100) kΩ
= -42 V/V
Transconductance Question 6:
A enhancement type N-Channel MOSFET is biased in linear region and is used as voltage controlled resistor. If the drain-source resistance is 500Ω for VGS = 2V then the drain-source resistance at VGS = 5 V is _________ Ω
Take VT = 0.5 V
Answer (Detailed Solution Below) 166 - 167
Transconductance Question 6 Detailed Solution
In linear region MOSFET drain current
In linear region with very small VDS the equation can be written as
VDS = 500 Ω for VGS = 2V
When VGS = 5V