Electronic Circuits II - Revision -1 / 16 -
T & F # 1 A bypass capacitor in a CE amplifier decreases the voltage gain. 2 If RC in a CE amplifier is increased, the voltage gain is reduced. 3 4 5 The load is the amount of current drawn from the output of an amplifier. In a CE amplifier, the gain can be stabilized by using a swamping resistor. In an amplifier, a coupling capacitor should appear ideally as a short to the signal. 6 r parameters include 7 h parameters are never specified on a datasheet. 8 The r parameter is the same as the h parameter hfe. 9 A bypass capacitor in a CE amplifier decreases the voltage gain. 10 If RC in a CE amplifier is increased, the voltage gain is reduced. 11 12 The load is the amount of current drawn from the output of an amplifier. In a CE amplifier, the gain can be stabilized by using a swamping resistor. 13 An emitter-follower is a CC amplifier. 14 A CC amplifier has high voltage gain. 15 A Darlington pair consists essentially of two CC amplifiers. 16 A CB amplifier has high current gain. 17 The overall voltage gain of a multistage amplifier is the product of the gains of each stage. 18 A differential amplifier amplifies the difference of two input signals. 19 CMRR is the common-mode resistance ratio. 20 The JFET always operates with a reverse-biased gate-to-source pn junction. 21 The channel resistance of a JFET is a constant. 22 The gate-to-source voltage of an n-channel JFET must be negative. 23 ID becomes zero at the pinch-off voltage. 24 VGS has no effect on ID. VGS(off ) and VP are always equal in magnitude but opposite in 25 polarity. -2 / 16 -
26 27 The JFET is a square-law device because of the mathematical expression of its transfer characteristic curve Forward transconductance is the change in drain voltage for a given change in gate voltage. 28 A D-MOSFET has a physical channel and an E-MOSFET has an induced channel. 29 ESD means electronic semiconductor device. 30 MOSFETs must be handled with care. 31 The parameters gm and yfs are the same. 32 The D-MOSFET can be operated in two modes. 33 An E-MOSFET operates in the depletion mode. MCQ # Question 1 If the transistor in Figure is exchanged for one with higher betas, Vout will -3 / 16 -
2 3 If C2 is removed from the circuit in Figure, Vout will If the value of RC in Figure is increased, Vout will -4 / 16 -
4 1 If the amplitude of Vin in Figure is decreased, Vout will If C2 in Figure is shorted, the average value of the output voltage will -5 / 16 -
2 3 If the value of RE in Figure is increased, the voltage gain will If the value of C1 in Figure is increased, Vout will 4 A small-signal amplifier (a) uses only a small portion of its load line (b) always has an output signal in the mv range (c) goes into saturation once on each input cycle (d) is always a common-emitter amplifier 5 6 7 A certain common-emitter amplifier has a voltage gain of 100. If the emitter bypass capacitor is removed, (a) the circuit will become unstable (b) the voltage gain will decrease (c) the voltage gain will increase (d) the Q-point will shift -6 / 16 -
8 9 10 11 12 13 14 15-7 / 16 -
1 2 If the value of RC in Figure is increased, the current gain will If C2 and C4 in Figure are increased in value, Vout will -8 / 16 -
3 4 If the value of R4 in Figure is reduced, the overall voltage gain will 5 6 7 8 9-9 / 16 -
10 1 1. The JFET is (a) a unipolar device (b) a voltage-controlled device (c) a current-controlled device (d) answers (a) and (c) (e) answers (a) and (b) 2 The channel of a JFET is between the (a) gate and drain (b) drain and source (c) gate and source (d) input and output 3 A JFET always operates with (a) the gate-to-source pn junction reverse-biased (b) the gate-to-source pn junction forward-biased (c) the drain connected to ground (d) the gate connected to the source 4 IDSS is (a) the drain current with the source shorted (b) the drain current at cutoff (c) the maximum possible drain current (d) the midpoint drain current 5 Drain current in the constant-current region increases when (a) the gate-to-source bias voltage decreases (b) the gate-to-source bias voltage increases (c) the drain-to-source voltage increases (d) the drain-to-source voltage decreases 6 7 6-10 / 16 -
8 9 If the value of RD in Figure is increased, ID will 10 For a certain p-channel JFET, VGS(off ) = 8 V. The value of VGS for an approximate midpoint bias is (a) 4 V (b) 0 V (c) 1.25 V (d) 2.34 V 11 The drain-to-source resistance in the ohmic region depends on (a) VGS (b) the Q-point values (c) the slope of the curve at the Q-point (d) all of these -11 / 16 -
12 If the drain current in Figure 8 17 is increased, VDS will 13 If the drain current in Figure is increased, VGS will 14 For VGS _ 0 V, the drain current becomes constant when VDS exceeds (a) cutoff (b) VDD (c) VP (d) 0 V -12 / 16 -
15 The constant-current region of a FET lies between (a) cutoff and saturation (b) cutoff and pinch-off (c) 0 and IDSS (d) pinch-off and breakdown 16 17 18 If the value of R2 in Figure is decreased, VG will 19 In a self-biased JFET, the gate is at (a) a positive voltage (b) 0 V (c) a negative voltage (d) ground -13 / 16 -
20 To be used as a variable resistor, a JFET must be (a) an n-channel device (b) a p-channel device (c) biased in the ohmic region (d) biased in saturation 21 When a JFET is biased at the origin, the ac channel resistance is determined by (a) the Q-point values (b) VGS (c) the transconductance (d) answers (b) and (c) 1 If the value of RG in Figure is increased, VG will 2 If the value of IDSS in Figure is increased, VDS will 3 A certain p-channel E-MOSFET has a If VGS _ 0 V, the drain current is (a) 0 A (b) ID(on) (c) maximum (d) IDSS -14 / 16 -
4 A certain p-channel E-MOSFET has a If VGS _ 0 V, the drain current is (a) 0 A (b) ID(on) (c) maximum (d) IDSS 5 If VGS in Figure is increased, ID will 6 If R2 in Figure opens, VGS will -15 / 16 -
7 A MOSFET differs from a JFET mainly because (a) of the power rating (b) the MOSFET has two gates (c) the JFET has a pn junction (d) MOSFETs do not have a physical channel 8 A D-MOSFET operates in (a) the depletion mode only (b) the enhancement mode only (c) the ohmic region only (d) both the depletion and enhancement modes 9 An n-channel D-MOSFET with a positive VGS is operating in (a) the depletion mode (b) the enhancement mode (c) cutoff (d) saturation 10 All MOS devices are subject to damage from (a) excessive heat (b) electrostatic discharge (c) excessive voltage (d) all of these 11 A certain D-MOSFET is biased at VGS _ 0 V. Its datasheet specifies IDSS _ 20 ma and The value of the drain current (a) is 0 A (b) cannot be determined (c) is 20 ma -16 / 16 -