1
GATE ECE 2014 Set 4
+2
-0.6
Consider the common-collector amplifier in the figure (bias circuitry ensures that the transistor operates in forward active region, but has been omitted for simplicity). Let IC be the collector current, VBE be the base-emitter voltage and VT be the thermal voltage. Also, 𝑔m and 𝑟o are the small-signal transconductance and output resistance of the transistor, respectively. Which one of the following conditions ensures a nearly constant small signal voltage gain for a wide range of values of RE?
A
$${g_m}{R_E} < < \,1$$
B
$${I_C}{R_E} > > \,{V_T}$$
C
$${g_m}{R_o} > > \,1$$
D
$${V_{BE}}\, > > {V_T}$$
2
GATE ECE 2014 Set 4
Numerical
+2
-0
A BJT in common-base configuration is used to amplify a signal received by a $$50\,\Omega$$ antena. Assume kT/q = 25 mV. The value of the collector bias current ( in mA ) required to match the input impedance of the amplifier to the impedance of the antena is ______.
3
GATE ECE 2014 Set 4
Numerical
+2
-0
For the common collector amplifier shown in the figure, the BJT has high $${V_{CE\left( {sat} \right)}},$$ and $${V_{BE}}$$ $$\, = \,\,0.7\,\,\,V$$. The maximum undistorted peak-to-peak output voltage $${V_o}$$ (in Volts) is _____.
4
GATE ECE 2014 Set 3
+2
-0.6
In the circuit shown, the silicon BJT has $$\beta \,\,\,\,50.\,\,\,\,\,$$ Assume $${V_{BE}}\,\,\, = \,\,\,0.7$$ and $${V_{CE\left( {sat} \right)}}\, = \,0.2V.$$ Which one of the following statements is correct ?
A
For $${R_c}\,\, = \,\,1k\Omega ,$$ the BJT operates in the saturation region.
B
For For $${R_c}\,\, = \,\,3k\Omega ,$$ the BJT operates in the saturation region
C
For For $${R_c}\,\, = \,\,20k\Omega ,$$ the BJT operates in the cut-off region.
D
For For $${R_c}\,\, = \,\,20k\Omega ,$$ the BJT operates in the linear region.
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