Introduction to Analog Electronics
Course‑level overview – suitable for beginners and as a refresher
1. What Is Analog Electronics?
| Aspect |
Description |
| Definition |
Deals with continuous‑time signals that can take any value within a range (voltage, current, charge, etc.). |
| Contrast with Digital |
Digital electronics uses discrete levels (0/1, high/low). Analog signals vary smoothly and often represent real‑world phenomena (sound, temperature, light intensity). |
| Typical Applications |
Audio amplifiers, sensor front‑ends, power supplies, radio frequency (RF) circuits, instrumentation, motor control, mixed‑signal ICs. |
2. Fundamental Concepts
| Concept |
Key Points |
Typical Symbol |
| Signal |
Continuous function of time, e.g., v(t) or i(t). |
– |
| Amplitude |
Height of the signal (peak, RMS, peak‑to‑peak). |
Vp, Vrms |
| Frequency |
Number of cycles per second (Hz). |
f |
| Phase |
Relative timing between two signals (degrees or radians). |
φ |
| Impedance (Z) |
Opposition to AC current; combines resistance (R) and reactance (X). |
Z = R + jX |
| Gain |
Ratio of output to input (voltage, current, power). Expressed as linear factor or dB. |
Av = Vout/Vin |
| Bandwidth |
Frequency range over which the circuit meets a specified performance (e.g., gain within –3 dB). |
– |
| Noise |
Unwanted random variations; characterized by spectral density, SNR, ENOB, etc. |
– |
3. Basic Passive Components
| Component |
Symbol |
Primary Function |
Typical Equation |
| Resistor |
R |
Limits current, creates voltage drops, sets bias points. |
V = I·R |
| Capacitor |
C |
Stores electric field energy, blocks DC, passes AC. |
I = C·dV/dt; XC = 1/(2πfC) |
| Inductor |
L |
Stores magnetic field energy, opposes changes in current. |
V = L·dI/dt; XL = 2πfL |
| Transformer |
– |
Couples magnetic flux between windings, provides impedance transformation and isolation. |
V₁/V₂ = N₁/N₂ |
Tip: In AC analysis, replace each component with its impedance (R, jX) and use Kirchhoff’s laws as you would for DC circuits.
4. Semiconductor Devices
| Device |
Symbol |
Operating Regions |
Typical Use in Analog Circuits |
| Diode |
D |
Forward, reverse (breakdown) |
Rectification, clipping, voltage reference |
| BJT (Bipolar Junction Transistor) |
Q |
Cut‑off, active, saturation |
Small‑signal amplification, switching |
| MOSFET (Metal‑Oxide‑Semiconductor FET) |
M |
Cut‑off, triode, saturation |
Voltage‑controlled resistor, amplifier, switch |
| JFET |
J |
Cut |
|