Hello. considering an integrated microprocessor chip in CMOS technology using Silterra 180nm PDK, for an integrated on-chip RF energy harvesting system. What is the difference between the specification of transistors when we design a simple analogue circuit such as LNA, and digital circuit such as memory chip and processor?
Hello Sir,
- Memory, digital and analog : That are basically 3 different area's.
- Like mentioned above, for digital, what matters most is speed and power, or - better - the speed/power tradeoff. Designs tend to use library standard cells, optimized for speed, power, area.
- For analog, there is a third factor which is important : Noise. You want low noise, stable gain, stable performance, high output impedance, low offset. When designing there, - and especially in the newer technologies like 28nm - , you need BIG transistors, in order to get good performance. The optimization is just different.
- Memory, SRAM or DRAM, that is special. It is basically part analog and part digital. The bitcell itself is digital, the readout (the sense amplifier) analog. The sense amplifier will here follow analog design strategy : It needs to be more accurate than 'pure' digital, but there is also a need to be fast and low power.
- Henri
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