← MES Jr. Grade
Past Questions
In 8085 stack pointer is
A)
4 bit
B)
8 bit
C)
16 bit
D)
32 bit
In the 8085 microprocessor, the stack pointer (SP) is a 16-bit register because it must hold a memory address. Since 8085 has a 16-bit address bus, the stack can be located anywhere in the 64 KB memory space. Therefore, the stack pointer is 16 bit. The other options are incorrect because 4-bit and 8-bit are too small to store a memory address, and 32-bit is not used in 8085.
The purpose of impedance matching in an amplifier circuit is to achieve
A)
high frequency
B)
reduced distortion
C)
maximum power transfer
D)
none of these
Impedance matching in an amplifier circuit is done so that the load receives the maximum possible power from the source or previous stage. According to the maximum power transfer theorem, this occurs when the load impedance matches the source impedance (or is the complex conjugate in AC circuits). It is not primarily for high frequency operation or reduced distortion.
In 8085, which addressing mode is also called inherent addressing?
A)
direct
B)
register
C)
implicit
D)
immediate
In 8085, the addressing mode in which the operand is implied by the instruction itself is called **implicit (inherent) addressing**. For example, instructions like CMC, RAL, and HLT do not specify an explicit operand.
Why others are incorrect:
- **direct**: the address of the operand is given explicitly in the instruction.
- **register**: the operand is in a register specified in the instruction.
- **immediate**: the data value itself is present in the instruction.
So, inherent addressing = implicit addressing.
The most commonly used bias in BJT amplifier circuit is
A)
voltage divider bias
B)
emitter bias
C)
collector bias
D)
collector feedback bias
In BJT amplifier circuits, the most commonly used biasing method is the voltage divider bias because it provides good thermal stability and keeps the operating point (Q-point) relatively stable against changes in transistor parameters like beta and temperature. Emitter bias, collector bias, and collector feedback bias are used in some circuits, but they are less common than voltage divider bias for general amplifier applications.
Which of the following is not a library string function in C?
A)
strlen
B)
strcpy
C)
strdup
D)
strbig
In C, `strlen`, `strcpy`, and `strdup` are known string-related library functions (though `strdup` is POSIX, not part of the C standard library). `strbig` is not a standard C library string function. Therefore, the correct answer is `strbig`.
Most of the memory chips with static RAM need
A)
2V supply
B)
5V supply
C)
12V supply
D)
none of above
Static RAM (SRAM) chips traditionally operate with a 5V power supply in standard computer architecture questions. 2V is too low for most conventional SRAM chips, and 12V is not the normal operating voltage for SRAM. Therefore, the correct answer is 5V supply.
The statement !( b < 5 ) in C means
A)
B = 5
B)
b > 5
C)
b >= 5
D)
b <= 5
In C, the expression `b < 5` is true when `b` is less than 5. The `!` operator negates this condition, so `!(b < 5)` means `b` is not less than 5, i.e. `b >= 5`. Hence the correct option is (c).
Which of the following is not an interrupt line in 8085?
A)
RST5.5
B)
RST7.5
C)
RST9.5
D)
TRAP
In the 8085 microprocessor, the interrupt lines are TRAP, RST 7.5, RST 6.5, RST 5.5, and INTR. Among the given options, RST9.5 is not an 8085 interrupt line. Therefore, the correct answer is RST9.5.
In deriving ac equivalent circuit for an amplifier circuit we short circuit all
A)
resistors
B)
inductors
C)
transistors
D)
capacitors
In the AC equivalent circuit of an amplifier, all DC sources are set to zero and coupling/bypass capacitors are treated as short circuits because their reactance is very low at signal frequencies. Inductors are not generally shorted; their treatment depends on the circuit and frequency. Resistors remain as they are, and transistors are not short-circuited.
Which of the following directives in 8085 assembler causes 2 bytes to be reserved in the memory?
A)
DS
B)
DB
C)
DW
D)
EQU
In 8085 assembler, **DW (Define Word)** reserves **2 bytes** of memory for a word-sized data item.
- **DB (Define Byte)** reserves 1 byte.
- **DS (Define Storage)** reserves a specified number of bytes, so it is not fixed at 2 bytes.
- **EQU** assigns a constant value and does not reserve memory.
Therefore, the correct answer is **DW**.
The 8257 chip is a
A)
Programmable interrupt controller
B)
programmable peripheral interface
C)
Programmable DMA controller
D)
programmable interval Timer
The Intel 8257 is a Programmable DMA (Direct Memory Access) controller used to transfer data between memory and I/O devices without continuous CPU involvement. Option (a) refers to 8259, the programmable interrupt controller; option (b) refers to 8255, the programmable peripheral interface; and option (d) refers to 8253/8254, the programmable interval timer.
The maximum theoretical efficiency for class A amplifier is
A)
12.5%
B)
25 %
C)
50%
D)
75%
For a class A amplifier, the maximum theoretical efficiency is 25% when using a resistive load. This is because the transistor conducts for the full 360° of the input cycle, causing significant power loss. Option (a) 12.5% is too low, while (c) 50% and (d) 75% are efficiencies associated with other amplifier classes or idealized push-pull arrangements, not class A.
Generally a servo motor operates at
A)
high torque and high speed
B)
low torque and low speed
C)
low torque and high speed
D)
Not provided
A servo motor is designed for precise control of position, speed, and acceleration. In general, it operates with low torque and high speed, especially in control applications where quick response is needed. Hence, option (c) is correct. Option (a) is incorrect because servo motors are not generally characterized by high torque and high speed together in basic exam context. Option (b) is incorrect because servo motors are not typically low speed. Option (d) is not applicable.
Which of the following 8085 instruction does not belong to arithmetic group?
A)
SHLD
B)
SUI
C)
ADC
D)
INR
In 8085, arithmetic instructions include operations like SUI (subtract immediate), ADC (add with carry), and INR (increment). SHLD is not an arithmetic instruction; it is a data transfer instruction used to store the HL pair directly into memory. Therefore, SHLD does not belong to the arithmetic group.
ALE stands for
A)
Address latch enable
B)
accumulator latch enter
C)
address latch enter
D)
accumulator latch enable
ALE in microprocessors stands for Address Latch Enable. It is a control signal used to latch the lower-order address from the multiplexed address/data bus. The other options are incorrect because ALE is not related to accumulator or 'enter'; it specifically refers to address latching.
If an OP-Amp has unity gain frequency of 1MHz, the cut off frequency at gain 10 will be
A)
100KHz
B)
1MHz
C)
10MHz
D)
90MHz
For a typical op-amp with a constant gain-bandwidth product, the product of closed-loop gain and cutoff frequency remains approximately equal to the unity gain frequency. Here, GBW = 1 MHz. At gain = 10, cutoff frequency = 1 MHz / 10 = 0.1 MHz = 100 kHz. So the correct option is (a). The other options do not satisfy the gain-bandwidth relation.
In a bridge rectifier circuit the r.m.s. value of input ac voltage is 10V. The PIV across each diode is
A)
7.07V
B)
10V
C)
14.14V
D)
28.28V
For a bridge rectifier, the peak inverse voltage (PIV) across each diode is equal to the peak value of the input AC voltage. Given the RMS input voltage is 10 V, the peak value is Vp = Vrms × √2 = 10 × 1.414 = 14.14 V. Hence, the PIV across each diode is 14.14 V. Option (a) is the RMS-to-peak conversion factor only, (b) is the RMS value itself, and (d) is twice the peak value, which is not applicable to a bridge rectifier.
A bypass capacitor produces
A)
dc ground
B)
ac ground
C)
both (a) & (b)
D)
none of these
A bypass capacitor is used to provide a low-resistance path for AC signals while blocking DC. In amplifier circuits, this makes the emitter/source node effectively at AC ground, improving gain. It does not create a DC ground because a capacitor blocks steady DC after charging. Hence, the correct answer is AC ground.
If the output current wave shape of class C circuit has a period 1µsec and pulse width of 0.006µsec, the duty cycle is
A)
6%
B)
0.6%
C)
0.06%
D)
0.006%
Duty cycle = (pulse width / period) × 100. Here, pulse width = 0.006 µs and period = 1 µs. So duty cycle = (0.006 / 1) × 100 = 0.6%. However, since the options include 0.06%, we must check the decimal carefully: 0.006 × 100 = 0.6, not 0.06. Therefore the correct computed value is 0.6%, which corresponds to option (b).
A push pull amplifier is a
A)
power amplifier
B)
voltage amplifier
C)
current amplifier
D)
both (a) and (c)
A push-pull amplifier is mainly used as a power amplifier because it delivers higher output power with better efficiency. It also acts as a current amplifier since it can supply a larger load current than the input stage. Therefore, the correct choice is both power amplifier and current amplifier.
The early effect in BJT is caused by
A)
fast turn on
B)
fast turn off
C)
large collector base reverse bias
D)
large emitter base forward bias
The Early effect (also called base-width modulation) in a BJT occurs when the collector-base reverse bias increases. This widens the depletion region at the collector-base junction, effectively reducing the base width and increasing collector current. Hence, it is caused by a large collector-base reverse bias. Options (a) and (b) relate to switching speed, not Early effect, and (d) is incorrect because the emitter-base junction is normally forward biased, but it does not cause the Early effect.
The open loop gain of an amplifier is 200. If negative feedback with β=0.2 is used, the closed loop gain will be
A)
200
B)
40.12
C)
4.878
D)
2.2
For a negative feedback amplifier, the closed-loop gain is
A_f = A / (1 + Aβ)
Given open-loop gain A = 200 and feedback factor β = 0.2:
Aβ = 200 × 0.2 = 40
So,
A_f = 200 / (1 + 40) = 200 / 41 = 4.878
Hence, the correct answer is 4.878. The other options do not match the standard negative feedback gain formula.
In which group of instructions condition flags are not affected?
A)
data transfer group
B)
arithmetic group
C)
logical group
D)
both (a) & (c)
In microprocessors, the data transfer group of instructions (e.g., MOV, MVI, LDA, STA, LXI) only transfers data and does not modify the condition flags. Arithmetic instructions generally affect flags like Carry, Zero, Sign, Parity, and Auxiliary Carry, and logical instructions also affect flags. Therefore, the correct answer is data transfer group.
The maximum number of characters for variable name in C language is
A)
4
B)
8
C)
12
D)
16
In many standard exam contexts, the maximum significant length of a C variable name is taken as 8 characters. Although modern C compilers may allow longer identifiers, older/typical MCQ conventions expect 8. Therefore, option (b) is correct. The other options 4, 12, and 16 are not the standard exam answer.
Which of the following instructions have only one operand?
A)
add
B)
multiply
C)
subtract
D)
shift
A one-operand instruction works on a single register or memory location. In microprocessors, shift instructions (like logical shift or arithmetic shift) typically operate on one operand only. Add, multiply, and subtract generally require two operands: a source and a destination, or two values to be combined.