Electrical, Electronic and Embedded Systems
Electrical, electronic and embedded systems questions bridge circuit analysis to microcontroller behaviour. The exam tests whether you can simplify a circuit, check an op-amp or transistor state, and reason about digital timing, conversion and communication rather than just quote component values.
Core rules
- KCL: currents leaving a node sum to zero; KVL: voltages around a loop sum to zero. Thevenin equivalents use open-circuit voltage and equivalent resistance with sources killed.
- Ideal op-amp in negative feedback: no input current and zero differential voltage. Inverting gain = −Rf/Rin; non-inverting gain = 1+Rf/Rg.
- A BJT is in saturation when both junctions are forward biased; do not assume β applies in saturation.
- An n-bit ADC with reference Vref has resolution Vref/2^n and code ≈ round(Vin/Vref × (2^n−1)) for a unipolar converter.
- Interrupts preempt the main loop; variables shared with an ISR need volatile or atomic handling.
Worked example
An inverting amplifier has Rin=2 kΩ, Rf=20 kΩ, ±12 V supplies, and Vin=0.2 V. Ideal gain is −20/2=−10, so Vout=−2 V, within the supply rails. If Vin=1.5 V, the ideal output is −15 V, but the op-amp clips near −12 V; the linear gain equation no longer applies.
Traps
- Forgetting that an ideal op-amp output cannot exceed its supply rails.
- Reversing the inverting gain sign or using Rin/Rf.
- Treating ADC resolution as Vref/(2^n−1) without checking the converter coding convention.
- Ignoring switch bounce, floating CMOS inputs, or missing decoupling.
- Confusing bit rate with baud rate when a symbol carries multiple bits.