I applied online and received an email from HR asking me to fill out a questionnaire and set up a first-round HR phone call. After this, I had three additional Skype technical interviews, each lasting one hour. I was then called onsite. They paid for everything, spending nearly $2000 on my interview process.

I was asked the following questions:

First Round - HR - 20 minutes

• Basic HR questions.

Second Round - Technical - 1 hour 10 minutes

• RC circuit: Transfer function; intuitively explain outputs for step and ramp inputs for low-pass, high-pass, and band-pass RC circuits.
• Comparator: Op-amp with positive feedback - hysteresis.
• Unity gain buffer with an input consisting of a sinusoid on a DC voltage: Clipping case first, then use a coupling capacitor to remove DC and get rid of coupling.
• How can you find the value of a resistor if an unknown resistor and voltmeter are given? Think from a system perspective; use a microcontroller and digital signals.

Third Round - 1 hour

• How does a proximity sensor work? Draw a simple circuit and demonstrate the working principle. Suppose one of the capacitors in your circuit is fabricated to an incorrect value, how do you troubleshoot it? Think from a system perspective.

Fourth Round - 45 minutes

• How does force touch work? Think from a system perspective. I described two methods, and then the interviewer asked me to state the advantages and disadvantages, focusing on reliability, power, and durability.

Onsite - 6 Technical, 1 HR interviews from 10:30 am to 5:30 pm - All are whiteboard interviews

• Probability questions: Basic - 4 children in a family, probability that at least one of them is a girl.
• Op-amp questions: Comparator - hysteresis - Draw input vs. output. Op-amp has resistors connected from the output to both the inverting and non-inverting terminals - does it have positive or negative feedback? What kind of feedback? Write the input vs. output transfer function.
• Switch capacitor questions; RC glitch questions; capacitance-to-voltage converters - charge sharing; transfer function.
• System-level solution for a scenario: You are given four noisy gyroscope outputs and need to send a preprocessed signal to a microcontroller. What preprocessing would you do?
• Interview with a mechanical engineer: Basic questions - A horizontal flagpole is hanging from a building, and one edge of the pole drooped due to its weight. What would you do to lessen the droop?
• Use a photodiode to control light in a room - Draw a circuit.
• Given an op-amp circuit that doesn't work properly, how do you troubleshoot it? Describe the correct methodology.

The emphasis is mainly on your approach rather than the correct or optimal solution. Study up on all kinds of op-amp sensor questions, RC circuits, and switched-capacitor circuits, and try to answer everything using op-amps. Also, try asking the interviewers a lot of questions to understand exactly what they are expecting, because the questions do not have unique solutions.