Analog and Digital Electronics
Analog and Digital Electronics tests op-amp configurations, diodes, BJT/MOSFET biasing, logic families, Boolean minimization, flip-flops and converters. ESE numericals are usually short: one gain, one logic function or one counter modulus.
Core rules
- Ideal op-amp with negative feedback: virtual short between inputs, zero input current. Inverting gain=-Rf/Rin; non-inverting gain=1+Rf/R1.
- Virtual ground fails without negative feedback or when the op-amp saturates.
- Boolean algebra: consensus, De Morgan, and Karnaugh-map grouping in powers of two. A 3-variable K-map can minimize to a single literal.
- Flip-flops: edge-triggered devices sample at the clock edge; setup and hold times must be met. Ripple counters have asynchronous propagation and decoding glitches.
- ADC resolution: one LSB=Vref/2^n for an n-bit converter.
Worked example
For an inverting amplifier, Rf=20 kohm, Rin=4 kohm, Vin=0.5 V. Gain=-20/4=-5; Vout=-2.5 V. The reasoning assumes an ideal op-amp, negative feedback and supply rails beyond 2.5 V; otherwise the output clips.
Traps
Using virtual ground in a comparator; forgetting the op-amp slew rate and saturation; treating a ripple counter modulus as 2^n when decoding resets earlier; and ignoring fan-out or unused CMOS inputs. In K-maps, do not group diagonally or in non-power-of-two groups.