Year 10 Mock Assessment Flashcards
What is the function of an AND gate?
An AND gate outputs HIGH (1) only when all its inputs are HIGH (1). The Boolean expression is Q = A • B.
What is the function of an OR gate?
An OR gate outputs HIGH (1) when at least one of its inputs is HIGH (1). The Boolean expression is Q = A + B.
What is the AND gate truth table in equation form?
0 • 0 = 0, 0 • 1 = 0, 1 • 0 = 0, 1 • 1 = 1
What is the OR gate truth table in equation form?
0 + 0 = 0, 0 + 1 = 1, 1 + 0 = 1, 1 + 1 = 1
What is the NAND gate truth table in equation form?
0 • 0 = 1, 0 • 1 = 1, 1 • 0 = 1, 1 • 1 = 0
What is the NOR gate truth table in equation form?
0 + 0 = 1, 0 + 1 = 0, 1 + 0 = 0, 1 + 1 = 0
What is Boolean algebra?
Boolean algebra is a mathematical system for logical operations using binary variables (0 and 1) and operators like AND (•), OR (+), and NOT (¬).
How can you create an AND gate using NAND gates?
An AND gate can be made by connecting two NAND gates in series: Q = NAND(NAND(A,B), NAND(A,B))
How can you create an OR gate using NAND gates?
An OR gate can be made with three NAND gates: Q = NAND(NAND(A,A), NAND(B,B))
What are the three main subsystems in a system block diagram?
- Input subsystem (sensors/switches) 2. Processing subsystem (logic circuits/microcontrollers) 3. Output subsystem (actuators/displays)
What is a monostable circuit?
A monostable circuit has one stable state and produces a single output pulse of fixed duration when triggered.
What is an astable circuit?
An astable circuit has no stable state and continuously oscillates between HIGH and LOW states, producing a square wave.
What does the output waveform of a monostable look like?
A single pulse with duration determined by RC components, returning to stable state after trigger.
What does the output waveform of an astable look like?
A continuous square wave with mark/space ratio determined by circuit components.
How do you calculate total resistance in series?
R_total = R1 + R2 + R3 + … (sum of all resistances)
How do you calculate total resistance in parallel?
1/R_total = 1/R1 + 1/R2 + 1/R3 + … (reciprocal of sum of reciprocals)
What is the voltage divider rule?
V_out = V_in × (R2 / (R1 + R2)) for two series resistors with output taken across R2.
What is Kirchhoff’s Voltage Law?
The sum of all voltages around any closed loop in a circuit equals zero.
What is Kirchhoff’s Current Law?
The sum of currents entering a junction equals the sum of currents leaving it.
What is the 555 timer IC?
An 8-pin integrated circuit capable of producing accurate time delays or oscillations in monostable/astable modes.
What is the function of pin 2 (Trigger) on a 555 timer?
When voltage here falls below 1/3 Vcc, it starts the timing cycle in monostable mode or triggers oscillation.
What is the function of pin 6 (Threshold) on a 555 timer?
When voltage here exceeds 2/3 Vcc, it resets the flip-flop ending the output pulse in monostable mode.
What is the function of pin 7 (Discharge) on a 555 timer?
Provides a path for capacitor discharge when the internal transistor is active (ON).
What is the function of pin 3 (Output) on a 555 timer?
Provides the output signal which can source or sink current to drive loads.
What is the function of pin 5 (Control Voltage) on a 555 timer?
Allows access to the internal voltage divider for modifying threshold/trigger levels.
What is the function of pin 1 (Ground) on a 555 timer?
Connected to 0V reference for the circuit.
What is the function of pin 8 (Vcc) on a 555 timer?
Positive power supply connection (typically 4.5-15V).
What is the function of pin 4 (Reset) on a 555 timer?
When pulled LOW (<0.7V), it forces output LOW regardless of other inputs.
What is the time period formula for a 555 monostable?
T = 1.1 × R × C (where R is in ohms, C in farads, T in seconds)
What is the formula for 555 astable frequency?
f = 1.44 / ((R1 + 2R2) × C)
What is the duty cycle formula for 555 astable?
Duty cycle = (R1 + R2) / (R1 + 2R2) × 100%
What is a capacitor?
A passive electronic component that stores electrical energy in an electric field between two conductive plates.
What is the symbol for a polarized capacitor?
A straight line (positive) next to a curved line (negative) for electrolytic capacitors.
What is the symbol for a non-polarized capacitor?
Two parallel straight lines of equal length.
How does a capacitor charge?
Exponentially through a resistor: Vc = V_supply × (1 - e^(-t/RC))
How does a capacitor discharge?
Exponentially through a resistor: Vc = V_initial × e^(-t/RC))
What is a Schmitt trigger?
A comparator circuit with hysteresis that converts analog signals to clean digital outputs with noise immunity.
What is a comparator?
An op-amp circuit that compares two voltages and outputs HIGH or LOW depending on which input is greater.
How does a comparator differ from a Schmitt trigger?
A comparator has no hysteresis - output changes immediately when inputs cross, making it sensitive to noise.
How can you make a NOT gate using a NAND gate?
Connect both inputs together: Q = NAND(A,A)
What is De Morgan’s Theorem?
¬(A + B) = ¬A • ¬B and ¬(A • B) = ¬A + ¬B (allows conversion between AND/OR forms using inversions)
What is the NAND gate redundancy principle?
Any logic function can be implemented using only NAND gates, making them functionally complete.
How many NAND gates are needed to make an XOR gate?
Four NAND gates can be combined to create an XOR function.
What is the output of a monostable if triggered during its timing cycle?
The output pulse continues for its full duration - it’s non-retriggerable unless specifically designed otherwise.
What determines the frequency of an astable multivibrator?
The RC time constant of the timing components and the specific circuit configuration.
What happens to 555 astable frequency if you increase the capacitor value?
The frequency decreases because the charging/discharging time increases.
What happens to 555 monostable pulse duration if you increase the resistor?
The pulse duration increases as the RC time constant grows larger.
What is the typical voltage range for the 555 timer?
4.5V to 15V, with some versions operating up to 18V.
Why use a Schmitt trigger instead of a regular comparator?
Schmitt triggers prevent multiple output transitions from noise on slowly changing input signals.
What is the typical hysteresis voltage in a Schmitt trigger?
Depends on design but often 0.5V-1V difference between upper and lower threshold voltages.
What is the minimum number of components needed for a 555 monostable?
Four: 555 IC, one resistor, one capacitor, and a power supply (plus optional trigger components).
What is the minimum number of components needed for a 555 astable?
Five: 555 IC, two resistors, one capacitor, and power supply.
What is the typical rise/fall time of 555 timer output?
About 100ns for standard 555, making it suitable for moderate-speed digital applications.
What is the purpose of the reset pin (4) in normal operation?
Should be tied to Vcc when not used to prevent accidental reset of the timer.
How can you synchronize multiple 555 timers?
Connect their reset pins together or use the output of one to trigger another.
What is the effect of adding capacitance to the control voltage pin (5)?
Improves noise immunity but adds slight delay to internal comparator responses.
How can you make a precision monostable with 555?
Use the control voltage pin with a precise reference voltage to set accurate thresholds.
What is the purpose of the 0.01μF capacitor often seen on 555 circuits?
Decoupling capacitor for the control voltage pin (5) to filter noise from internal reference.
What is the advantage of using NAND gates for all logic?
Simplifies inventory (only one gate type needed) and takes advantage of NAND’s functional completeness.
How can you test a 555 timer circuit?
Check power supply, verify trigger/threshold voltages with oscilloscope, and monitor output waveform.
How can you improve 555 timer stability?
Use stable components (metal film resistors, polypropylene capacitors), regulate supply voltage.
What is a typical application of a monostable circuit?
Debouncing switches, creating fixed-duration pulses from momentary inputs, time delay generation.
What is a typical application of an astable circuit?
Clock generation, LED flashers, tone generation, PWM control.
What is the advantage of Schmitt trigger inputs in digital systems?
Noise immunity and clean transitions even with slow or noisy input signals.
What is a MOSFET and what are its main types?
A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a voltage-controlled transistor. Main types: 1) Enhancement mode (normally off) 2) Depletion mode (normally on). Further divided into N-channel and P-channel varieties.
What are the three terminals of a MOSFET?
1) Gate (control terminal) 2) Drain (output terminal) 3) Source (common terminal). The body/substrate is sometimes considered a fourth terminal.
How does a MOSFET work as a switch?
When V_GS exceeds threshold voltage (for enhancement MOSFET), it creates a conductive channel between drain-source, allowing current flow. Below threshold, it acts as open circuit.
What is the key advantage of MOSFETs over BJTs?
MOSFETs are voltage-controlled (almost no gate current) with very high input impedance, making them more efficient for switching applications.
What is an operational amplifier (op-amp)?
A high-gain DC-coupled differential amplifier with two inputs (inverting and non-inverting) and one output, typically requiring dual power supplies.
What are the golden rules of op-amp operation?
1) Infinite input impedance (no current flows into inputs) 2) Infinite open-loop gain 3) Zero output impedance 4) Inputs will equalize when in negative feedback configuration.
What is the typical symbol for an op-amp?
A triangle with two inputs on left (- for inverting, + for non-inverting), output on right, and power supply connections (V+ and V-) at top and bottom.
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What is the circuit symbol for an AND gate?
A D-shaped symbol with two or more input lines on the flat side and one output line on the curved side. Inputs: left side, Output: right side.
What is the circuit symbol for an OR gate?
A curved/shield-shaped symbol with two or more input lines on the concave side and one output line on the pointed convex side.
What is the circuit symbol for a NAND gate?
Same as AND gate but with a small circle (inversion bubble) at the output, right after the D-shape.
What does the 555 timer IC symbol look like in circuit diagrams?
Usually shown as a rectangular block with 8 pins labeled: 1-GND, 2-Trigger, 3-Output, 4-Reset, 5-Control, 6-Threshold, 7-Discharge, 8-Vcc.
What is the symbol for a Schmitt trigger?
Typically shown as a triangular comparator symbol with a hysteresis loop inside (∞-shaped curve between inputs).
What is the symbol for a non-inverting op-amp?
Triangle with (+) input on left, (-) below, output on right, power rails top/bottom. Non-inverting input marked ‘+’.
What is the symbol for a MOSFET (N-channel enhancement)?
Three-terminal symbol: Gate (vertical line), Drain (upward arrow), Source (downward arrow). Dashed channel line for enhancement mode.
How is a polarized capacitor represented?
Two parallel lines: one straight (positive/anode), one curved (negative/cathode) for electrolytics.
What does the astable multivibrator symbol look like?
No standard symbol - typically shown as a 555 or op-amp circuit with two capacitors forming the timing network.
What is the comparator circuit symbol?
Similar to op-amp but often without power pins in schematics - triangle with (+) and (-) inputs, single output.
