Form No. T651
Philadelphia University Student Name:
Faculty of Engineering Student Number:
Dept. of Communications and Electronics Engineering
Course Title: Digital Electronics & Techniques
Course No: 650344, 630330Lecturer: Dr. Wagah F. Mohammad
Section:
Question:
This question is general: Tick (√) the correct answer.
1- Large scale integration refers to a chip containing
· 103-104 .
· 102-103 .
· 104-105 .
2- Very large scale integration refers to a chip containing
· 103-104 .
· 102-103 .
· 104-105 .
3- - Medium scale integration refers to a chip containing
· 103-104 .
· 102-103 .
· 104-105 .
4- Digital electronics is the branch of electronics concerned with electronic system exhibits:
· Linear behavior.
· Switching behavior.
· Exponential behavior.
5- Periodic pulse waveform is a repetitive pulse with predetermined:
· Frequency.
· Voltage.
· Current
6- If the voltage across the capacitor is constant that means the current through the capacitor is:
· Constant.
· Maximum.
· Zero.
7- The output signal of an RC circuit reaches the steady state at
· Ts=Tc.
· Ts= 5Tc.
· Ts=10Tc.
8- In RC circuit the voltage across the capacitor at t=0 is;
· Final value.
· Initial value.
· Zero.
9- When time constant of the circuit (Tc) is much shorter than signal transion time (Tup) of the input, the circuit output will.
· Little effect.
· High effect.
· No effect.
10- When time constant of the circuit (Tc) is larger than signal transion time (Tup) of the input , the circuit output will
· Attenuated.
· Has little effect
· Has very fast transion time.
11- The voltage across the capacitor (Vc) in an RC circuit can be expressed as follow:
· Vc= Vf+ (Vin-Vf) e-t/RC.
· Vc= Vf- (Vin-Vf) e-t/RC.
· Vc= Vf+ (Vin-Vf) e-RC/t.
12- The output of resistive load in an RC circuit tends to :
· Slow down the output.
· Attenuate the output.
· Increase the time constant of the circuit.
13- As the value of the load resistance in RC circuit is decreased the steady state time of the circuit is.
· Increased.
· Decreased
· Not effected
14- The resistance of the forward biased diode is:
· Very small nearly zero.
· Medium in KΩ.
· Very large nearly infinity.
15- Because the capacitance of the diode is very small, the time constant will be:
· Very short time.
· Medium time in sec.
· Very long time.
16- For the transistor in active region, the base –collector junction:
· Forward biased.
· Not biased.
· Reverse biased.
17- For the transistor in saturation region, the base –collector junction:
· Forward biased.
· Not biased.
· Reverse biased.
18- When the transistor is turned off, the delay time (Td) represent the time:
· To remove the access charges from the base.
· To add the access charges from the base.
· To charge the junction capacitors.
19- When the transistor is turned on , the storage time (Ts) represent the time:
· To remove the access charges from the base.
· To add the access charges from the base.
· To charge the junction capacitors.
20- Bipolar transistor operated in saturation region when the base –collector junction is:
· Reverse biased
· Forward biased.
· Not biased.
21- The reverse diode resistance is:
· Very low.
· Medium.
· Very high.
22- The total turn off time (toff) of the transistor is the sum of:
· ts + tr.
· tr + tf.
· td + tf.
23- When the transistor is saturated, any base current above the value of Ibsat, the Icsat will be
· Increased.
· Decreased.
· Kept constant.
24- When the transistor is saturated, any base current above the value of Ibsat, as a result there is an excess charges in the base will be:
· Removed.
· Stored.
· not effected
25- Faster turn on of the transistor requires the value of Rb to be :
· Large.
· Small.
· Any value.
26- Faster turn off of the transistor requires the value of Rb to be :
· Large.
· Small .
· Any value.
27- Choosing high value of the load resistor (Rc) the rise time of the circuit is;
· Long.
· Short.
· Not effected
28- Choosing high value of the load resistor (Rc) the high output of the circuit is;
· Higher.
· Lower.
· Not changed
29- Choosing small value of the load resistor (Rc), the current that flow through the output transistor is:
· Large.
· Small.
· Not changed
30- Choosing small value of the load resistor (Rc), the noise margins will be :
· Shallower.
· Deeper.
· Not effected
31- High noise margin of any digital circuit is the difference between:
· VOH - VOL.
· VIH – VIL.
· VOH - VIH
32- Fan-out of a digital circuit is defined as:
· IO/II.
· VO/VI.
· VO/IO.
33- When the digital output is low, the current will flow:
· Outside the circuit (Sourcing current).
· Inside the circuit (Sinking Current).
· No current will flow.
34- The temperature range of 74 TTL is
· 0 < ToC<70.
· 0 < ToC<125.
· -50< ToC<70
35- The temperature range of 54 TTL is
· 0 < ToC<70.
· 0 < ToC<125.
· -50< ToC<125
36- The propagation delay time of advance shcottky TTL is
· Very large.
· Normal.
· Very small
37- The power dissipation advance low power shcottky TTL is;
• Very large.
• Normal.
• Very small
38- At high output TTL too many loads causing larger drop across R2, T3and D thereby Voh is :
· Increased
· Decreased.
· Not effected
39- At low output TTL too many loads causing larger drop across T4 thereby Vol is :
· Increased
· Decreased.
· Not effected
40- Unused inputs of NOR gates should be connected to the:
· Power supply.
· Used input.
· Left floating.
41- One of the following digital outputs cannot be Wired-Anding:
· Totem-pole output.
· Open-collector output.
· Tri-state output.
42- The job of top transistor (T3) in totem pole output is to connect the output to:
· Vcc.
· GND.
· Neither Vcc nor GND.
43- The job of diode (D) in the totem pole output is to make the transistors:
· T3 is switching faster thanT4.
· T4 is switching faster than T3.
· T3 & T4 switches at the same time.
44- In order to increase the switching speed of MOSFET logic, the channel length must be:
· Increased.
· Decreased.
· Not changed.
45- The number of transistors needed to build n-input of dynamic-NMOS Inverter is:
A- 2n .
B- n2.
C- n + 2.
46- The high output voltage of NMOS Inverter with Depletion load is:
A- VOH = VDD - Vt.
B- VOH = VDD + Vt.
C- VOH = VDD.
47- For the following digital signal: the duty cycle is:
· ton + toff
· ton / toff
· ton/ T
48- The time needed for RC circuit to reach a steady state is:
· T = 0.7 RC
· T = eRC
· T = 5RC
49- The junction (s) in Schottky diodes is (are) formed between:
· Semiconductor-Semiconductor layers.
· Metal-Semiconductor layers.
· Metal-Insulator layers.
· Metal-Insulator-Semiconductor layers.
50- Schottky devices reduce the storage time delay (ts) by:
· Allowing the transistor to go deeply in saturation.
· Not allowing the transistor to go deeply in saturation.
· Allowing the transistor to go very fast to cutoff.
51- The number of transistors needed to build n inputs of dynamics NMOS gate is:
· 2n
· n+2
· 2n
52- In the logic circuit noise margin diagram: any input voltage lower than VIH and greater than VIL is considered:
· Logic one (high level).
· Logic zero (low level).
· Unpredictable (neither one nor zero).
53- Totem pole output with the presence of D between T3 & T4: the transistors
· Can't be reverse in the same time.
· Can't be forward in the same time.
· Can be forward in the same time.
54- Emitter coupled logic (ECL) is a type of difference amplifier because the output is proportional to the difference between the:
- Two inputs.
- Two outputs.
- Output & input
55- The fastest of logic families is:
· MOSFETL
· ECL
· TTL.
56- The advantages of connecting NEMOS & PEMOS in Transmission gate is to transmit:
· High level voltage.
· Entire input voltage.
· Zero level voltage.
57- Monostables multivibraters are a digital circuit has:
· No stable state.
· One stable state.
· Two stable states
58- ROM digital circuit is composed of two digital arrays:
· Programmed AND array & fixed OR array.
· Fixed AND array & programmed OR array.
· Programmed AND & OR arrays.
59- Digital signal vary between two levels;
· Smoothly (linearly).
· Continuously (Sine signal).
· Abruptly (In discrete manner).
60- One of the digital family can be utilized in VLSI circuits:
· TTL.
· ECL
· MOSFET.
61- If the voltage across the capacitor is constant: the current will be equal to:
· V/Xc.
· Maximum.
· Zero.
62- ECL is the fastest of all logic families due to the eliminating of storage time of the input transistor because they are prevented from going to:
· Cutoff.
· Active.
· Saturation.
63- In order to make the MOSFET logic circuit switching very fast the load should be:
· Resistive.
· Capacitive.
· Transistor current source.
64- The On resistance (Ron) of MOS transistor varies with channel length (L):
· Linear.
· Inverse.
· Exponential.
65- The On resistance (Ron) of MOS transistor varies with channel width (W):
· Linear.
· Inverse.
· Exponential.
66- MOSFET transistors have very small ON resistance (Ron) at:
· Cutoff region.
· Saturation (pinch off) region.
· Triode (linear or Ohmic) region.
67- In order to make MOSFET transistor switch ON & OFF very fast, the gain must be:
· Increases.
· Decreases.
· Kept constant.
68- The use of depletion MOS as the load element makes the noise margins of digital circuits:
· Wider.
· Narrower.
· Not affected.
69- Which gate has the biggest area
· NEMOS with enhancement load
· NEMOS with depletion load.
· CMOS
70- Which gate transmit the total input signal.
· NEMOS with enhancement load
· NEMOS with depletion load.
· CMOS
71- The main disadvantage of dynamic storage cell memory is;
· Occupy large silicon area.
· Use complex circuitry.
· Loose data due to leakage.
72- The main disadvantage of static storage cell memory is;
· Occupy large silicon area.
· Retain the data.
· Need refreshment due to data leakage.
73- The main advantage of dynamic storage cell memory is.
· Retain the data for very long time.
· Occupy small silicon area.
· Use complex circuitry.
74- The main advantage of static storage cell memory is.
· Retain the data for very long time.
· Occupy small silicon area.
· Use very simple circuitry.
75- Transmission CMOS gate is created by connecting NEMOS in parallel with PEMOS in order to transmit:
· The high level voltage.
· The low level voltage.
· The entire level voltage.
76- PAL digital circuit is composed of two digital arrays:
· Programmed AND array & fixed OR array.
· Fixed AND array & programmed OR array.
· Programmed AND & OR arrays.
77- PLA digital circuit is composed of two digital arrays:
· Programmed AND array & fixed OR array.
· Fixed AND array & programmed OR array.
· Programmed AND & OR arrays.
78- The output word width of 210x8 ROM is:
· 210 bits.
· 10 bits.
· 8 bits.
79- The number of unique addresses of 210x8 ROM is:
· 210 bits.
· 10 bits.
· 8 bits.
80- The number of words of 210x8 ROM is:
· 210 words.
· 10 words.
· 210x8 words.
81- The capacity (number of bits) of 210x8 ROM is:
· 210 bits.
· 210x8 bits.
· 8 bits
82- The data in Random Access Memory (RAM) can be:
· Read only.
· Write only.
· Read or Write only.
· Read and/or Write.
83- The storage cells in static RAMs are;
· Flip-Flop cells.
· Capacitor cells.
· Mixed Flip-Flops & capacitor cells.
84- The storage cells in Dynamic RAMs are;
· Flip-Flop cells.
· Capacitor cells.
· Mixed Flip-Flops & capacitor cells.
85- One of the following storage cells need a refresh signal to prevent data leakage:
· Dynamic storage cell.
· Static storage cell.
86- Monostables multivibraters has:
· One stable state.
· Two stable states.
· No stable state.
87- Bistables multivibraters has:
· One stable state.
· Two stable states.
· No stable state.
88- Astables multivibraters has:
· One stable state.
· Two stable states.
· No stable state.
89- The duty cycle of monostables output is proportional to:
· Width of the input signal.
· External RC circuit.
· Internal RC circuit.
90- Retriggerable monostables respond to the input signal as long as the output in:
· Stable state.
· Quisistable state.
· Both states.
91- Nonretriggerable monostables respond to the input signal as long as the output in:
· Stable state.
· Quisistable state.
· Both states.
92- The width of hysteresis loop of Schmitt trigger circuit that switch ON at 5V and OFF at 3V is:
· Two Volts.
· Three Volts.
· Five Volts.
93- 555 multivibraters can be connected to perform:
· Monostables multivibraters only.
· Astables multivibraters only.
· Monostables & Astables multivibraters.
94- The control input of the 555 multivibrator is used to apply a voltage to the control input in order to change: