1
GATE ECE 2009
+2
-0.6
Consider the CMOS circuit shown, where the gate voltage of the n-MOSFET is increased from zero, while the gate voltage of the p-MOSFET is kept constant at 3 V. Assume that, for both transistors, the magnitude of the threshold voltage is 1 V and the product of the transconductance parameter and the $$\left(\frac WL\right)$$ ratio, i.e. the quantity $$\mu C_{ox}\left(\frac WL\right)$$ , is 1 mAV-2.
For small increase in VG beyond 1 V, which of the following gives the correct description of the region of operation of each MOSFET?
A
Both the MOSFETs are in saturation region
B
Both the MOSFETs are in triode region
C
n-MOSFET is triode and p-MOSFET is in saturation region
D
n-MOSFET is in saturation and p-MOSFET is in triode region
2
GATE ECE 2009
+2
-0.6
Consider the CMOS circuit shown, where the gate voltage of the n-MOSFET is increased from zero, while the gate voltage of the p-MOSFET is kept constant at 3 V. Assume that, for both transistors, the magnitude of the threshold voltage is 1 V and the product of the transconductance parameter and the $$\left(\frac WL\right)$$ ratio, i.e. the quantity $$\mu C_{ox}\left(\frac WL\right)$$ , is 1 mAV-2.
Estimate the output voltage V0 for VG =1.5 V. [Hints: Use the appropriate current-voltage equation for each MOSFET, based on the answer]
A
$$\left(4-\frac1{\sqrt2}\right)V$$
B
$$\left(4+\frac1{\sqrt2}\right)V$$
C
$$\left(4-\frac{\sqrt3}2\right)V$$
D
$$\left(4+\frac{\sqrt3}2\right)V$$
3
GATE ECE 2008
+2
-0.6
Two identical NMOS transistors M1 and M2 are connected as shown below. Vbias is chosen so that both transistors are in saturation. The equivalent gm of the pair is defined to be $$\frac{\partial I_{out}}{\partial v_i}$$ at constant Vout. The equivalent gm of the pair is
A
The sum of individual gm’s of the transistors
B
The product of individual gm’s of the transistors
C
Nearly equal to the gm of M1
D
Nearly equal to gm/g0 of M2
4
GATE ECE 2008
+2
-0.6
For the circuit shown in the following figure, transistors M1 and M2 are identical NMOS transistors. Assume that M2 is in saturation and the output is unloaded The current Ix is related to Ibias as
A
$$I_x\;=I_{bias}\;+\;I_s$$
B
$$I_x\;=I_{bias}\;$$
C
$$I_x\;=I_{bias}\;-\;I_s$$
D
$$I_x\;=I_{bias}\;\left(V_{DD}\;-\frac{V_{out}}{R_E}\right)$$
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