Flash ADC front end
13 parts
How the fastest ADCs work: a resistor string sets three references — 1.25, 2.50 and 3.75 V — and three op-amps running open-loop as comparators convert a 0.1–4.9 V triangle into a thermometer code, all levels compared at once. A NOR/NOT chain then encodes the LSB of the 2-bit binary result, and its edges land exactly on the references: high from 1.25 V to 2.5 V and again above 3.75 V. The op-amps are rail-limited behavioural macromodels (rails set to 0/5 V so they put out logic levels) and the gates are 2.5 V-threshold logic macromodels with a one-solver-step delay — not transistor-level designs.
- V1 2.4V·400Hz
- V2 5V
- R1 1kΩ
- R2 1kΩ
- R3 1kΩ
- R4 1kΩ
- OP1
- OP2
- OP3
- NOT1
- NOR1
- NOR2
- NOT2
