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6581 Opamps
The designers were not able to implement real OpAmps, so the amplifiers in the 6581 are self-centering inverters.
Each of the 6 amplifiers is built from 4 NMOS FETS, did draw white boxes around the FETs in this picture:
Schematic of an amplifier:
Layout for all the amplifiers is pretty much the same, it's just mirrored sometimes to make better use of the space on the silicon.
Clock
Reset
Address Decoders
Data Bus
Registers
Oscillator
Pulse Waveform
Triangle Waveform
Noise Generator
Wave Selector
Envelope Overview
Envelope Counter
Sustain Comparator
ADSR registers
Counter Logic
Exponential Divider
LFSR15 counter
LFSR5 counter
Analog stage overview
6581 DACs
6581 Opamps
6581 Filter overview
6581 Audio output
8580 DACs
8580 Virtual ground
8580 AC Voltage divider
8580 Opamps
8580 Filter overview