BJT and FET · Electronic Devices and VLSI · GATE ECE

An ideal MOS capacitor (p-type semiconductor) is shown in the figure. The MOS capacitor is under strong inversion with V_G = 2V. The corresponding inversion charge density (Q_IN) is 2.2 $$\mu$$C/cm². Assume oxide capacitance per unit area as C_ox = 1.7 $$\mu$$F/cm². For V_G = 4V, the value of Q_IN is __________ $$\mu$$C/cm² (rounded off to one decimal place).

Consider the circuit shown in the figure. Assume base-to-emitter voltage V_BE=0.8 V and common base current gain $$\left(\alpha\right)$$ of the transistor is unity. The value of the collector-to–emitter voltage V_CE (in volt) is _______.

An npn bipolar junction transistor (BJT) is operating in the active region. If the reverse bias across the base-collector junction is increased, then

For a narrow base PNP BJT, the excess minority carrier concentration ($$\bigtriangleup n_E$$ for emitter, $$\bigtriangleup p_B$$ for base, $$\bigtriangleup n_E$$ for collector) normalized to equilibrium minority carrier concentration ($$\bigtriangleup n_{E0}$$ for emitter, $$\bigtriangleup p_{B0}$$ for base, $$\bigtriangleup n_{C0}$$ for collector) in the quasi-neutral emitter, base and collector regions are shown below. Which one of the following biasing modes is the transistor operating in?

The figure shows the I-V characteristics of a solar cell illuminated uniformly with solar light of power 100 mW/cm². The solar cell has an area of 3 cm² and a fill factor of 0.7. The maximum efficiency (in %) of the device is __________.

The Ebers-Moll model of a BJT is valid

If the base width in a bipolar junction transistor is doubled, which one of the following statements will be TRUE?

In the circuit shown in the figure, the BJT has a current gain (β) of 50. For an emitter-base voltage V_EB = 600 mV, the emitter-collector voltage V_EC(in Volts) is ______.

An increase in the base recombination of a BJT will increase

For a BJT the common base current gain $$\alpha$$ = 0.98 and the collector base junction reverse bias saturation current I_CO = 0.6μA. This BJT is connected in the common emitter mode and operated in the active region with a base drive current I_B=20μA. The collector current IC for this mode of operation is

If the transistor in Figure is in saturation, then

MOSFET can be used as a

The breakdown voltage of a transistor with its base open is BV_CEO with emitter open is BV_CBO, then

A BJT is said to be operating in the saturation region if

The Early-Effect in a bipolar junction transistor is caused by

The Ebers-Moll model is applicable to

The transit time of the current carriers through the channel of an FET decides its ____________characteristics.

Channel current is reduced on application of a more positive voltage to the gate of a depletion mode n-channel MOSFET.

The injected excess electron concentration profile in the base region of an npn BJT, biased in the active region, is linear, as shown in the figure. If the area of the emitter-base junction is 0.001 cm², µ_n = 800 cm²/(V-s) in the base region and depletion layer widths are negligible, then the collector current I_c (in mA) at room temperature is __________. (Given: thermal voltage V_T = 26 mV at room temperature, electronic charge q = $$1.6\times10^{-19}\;C$$ )

An npn BJT having reverse saturation current $$I_s\;=\;10^{-15}\;A$$ is biased in the forward active region with V_BE = 700 mV. The thermal voltage (V_T) is 25 mV and the current gain (β) may vary from 50 to 150 due to manufacturing variations. The maximum emitter current (in μA) is _____.

Consider two BJT's biased at the same collector current with area A₁ = 0.2 μm × 0.2 μm and A₂ = 300 μm × 300 μm. Assuming that all other device parameters are identical, kT/q = 26 mV, the intrinsic carrier concentration is 1 × 10¹⁰ cm^-3, and q = 1.6 × 10^-19 C, the difference between the base-emitter voltages (in mV) of the two BJT's (i.e., V_BE1 – V_BE2) is___________.

The channel resistance of an N-channel JFET shown in the figure below is 600 W when the full channel thickness (t_ch) of 10 μm is available for conduction. The built-in voltage of the gate P⁺N junction (V_bi) is -1 V. When the gate to source voltage (V_GS) is 0 V, the channel is depleted by 1 μm on each side due to the built in voltage and hence the thickness available for conduction is only 8 μm The channel resistance when V_GS = -3 V is

The channel resistance of an N-channel JFET shown in the figure below is 600 W when the full channel thickness (t_ch) of 10 μm is available for conduction. The built-in voltage of the gate P⁺N junction (V_bi) is -1 V. When the gate to source voltage (V_GS) is 0 V, the channel is depleted by 1 μm on each side due to the built in voltage and hence the thickness available for conduction is only 8 μm The channel resistance when V_GS = 0 V is

In a uniformly doped BJT, assume that N_E, N_B and N_C are the emitter, base and collector dopings in atoms/cm³, respectively. If the emitter injection efficiency of the BJT is close unity, which one of the following conditions is TRUE?

The DC current gain ($$\beta$$) of a BJT is 50. Assuming that the emitter injection efficiency is 0.995, the base transport factor is:

An n-channel JEFT has I_DSS = 2 mA and V_p = −4 V. It's transconductance g_m (in mA/V) for an applied gate-to-source voltage V_GS of –2V is:

An n-channel JFET has a pinch-off voltage V_P = -5 V, V_DS(max) = 20 V and g_m = 2 mA/V. The minimum ‘ON’ resistance is achieved in the JEFT for

In a transistor having finite B, the forward bias across the base emitter junction is kept constant and the reverse bias across the collector base junction is increased. Neglecting the leakage across the collector base junction and the depletion region generating current, the base current will __________. (increase/decrease/remain constant).