- The article explains reverse engineering of analog chips using the Philips TDA7000 FM radio receiver as an example, a 1977 chip with over 100 transistors and single-layer metal.
- Key components identified on the die include NPN transistors (rectangular, vertical structure), PNP transistors (circular, lateral), resistors (zig-zag P-type silicon), and junction capacitors (comb-shaped reverse-biased diodes).
- Common analog circuits are described: emitter follower (voltage follower with current amplification), current mirror (clones reference current), current source/sink, differential pair amplifier (two transistors with connected emitters), and Gilbert cell multiplier (four-quadrant multiplication).
- The chip uses superheterodyne with a 70 kHz intermediate frequency, a quadrature detector for FM demodulation, and a voltage-controlled oscillator with varicap diodes for frequency tracking.
- Reverse engineering tips include using datasheets, mapping pinouts, tracing power/ground, numbering components, using KiCad for schematics, and simulating with LTspice.
- The TDA7000 became a commercial success after initial rejection, selling over 5 billion units, and is popular for hobbyist radio projects due to its simplicity.