STMicroelectronics Analog Design Engineer Interview Questions and Answers

General aptitude questions. Easy to solve. Didn’t take much time

Q1. Explain operation of rc circuit
Ans. 
An RC circuit consists of a resistor and a capacitor connected in series or parallel, used for filtering, timing, and signal processing.
• RC circuit operation is based on the charging and discharging of the capacitor through the resistor.

• When a voltage is applied to the circuit, the capacitor charges up to the applied voltage through the resistor.

• The time constant (RC) determines how quickly the capacitor charges or disc...read more
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Q2. Draw waveform for diode
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A diode waveform typically shows a voltage drop when forward biased and no current flow when reverse biased.
• Forward biased: voltage drop across diode, current flows

• Reverse biased: no current flow, diode acts as open circuit
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Q1. Questions based on my project
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Analog circuits , opamp, mosfets , Rc circuits

Q1. Nmos design and working
Ans. 
NMOS (N-channel Metal-Oxide-Semiconductor) is a type of MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) that uses n-type semiconductor for the channel.
• NMOS transistors are used in digital and analog circuits for switching and amplification.

• In NMOS design, the gate is made of metal, the insulator is made of oxide, and the semiconductor is n-type.

• NMOS transistors operate by applying a voltage to the gate termi...read more
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Q2. CMOS circuit and design along with VTC characteristics
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CMOS circuits are widely used in integrated circuits for their low power consumption and high noise immunity. VTC characteristics show the relationship between input and output voltage.
• CMOS circuits consist of complementary pairs of p-type and n-type MOSFETs, allowing for low power consumption and high noise immunity.

• VTC (Voltage Transfer Characteristic) shows the relationship between input and output voltage in a CMOS...read more
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Contained analog basics

Q1. Cmos , Nmos characteristics in depth along with output and input wave forms, some basic digital questions , questions on current mirrors .
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It was easy with some tricky question

Q1. Question on MOSFET Electrical network Analog electronics
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Q2. Why cascade structure is used
Ans. 
Cascade structure is used to improve gain, bandwidth, and linearity of amplifiers.
• Cascade structure combines multiple amplifier stages to achieve higher overall gain.

• Each stage can be optimized for a specific frequency range, improving bandwidth.

• Cascade structure also reduces distortion and improves linearity.

• Examples include cascode amplifiers and differential amplifiers.

• Cascade structure is commonly used in high-freq
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Q3. Why MOSFET over others
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90 minutes with 20 questions of Analog and Aptitude each. Topics are Basic Network Theory, Diode, Op-amps, etc. Topics may vary place-to-place.

Q1. Questions are cumulative: Draw a Lowpass filter (RC)
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Q2. Add capacitor parallel to one resistor and tell frequency response
Ans. 
Adding a capacitor in parallel to a resistor changes the frequency response of the circuit.
• The cutoff frequency of the circuit decreases as the capacitance increases.

• The circuit becomes a high-pass filter with a -20dB/decade slope above the cutoff frequency.

• The impedance of the capacitor decreases as frequency increases, allowing more current to flow through the circuit.

• The resistor and capacitor form a voltage divider...read more
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Q3. Add resistor to the capacitor and tell frequency response
Ans. 
Adding a resistor to a capacitor changes the frequency response of the circuit.
• The cutoff frequency of the circuit decreases with increasing resistance.

• The circuit becomes more attenuative at higher frequencies.

• The time constant of the circuit increases with increasing resistance.

• The circuit becomes more stable and less prone to oscillation.

• Example: A low-pass filter with a 10uF capacitor and a 1kohm resistor has a cut
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Q4. T-flip flop mod3 counters and reset
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Q5. A tricky diode based network question with both cases(ideal and non-ideal diode)
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Q6. Aptitude question of 1000 bottles and one poisoned
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