mbright
Junior Member level 1
how to become an analog ic design
Seems to me that quite a few ppl on this board r doing analog IC design or relative stuff.
Let us share and discuss some idea and prospective in the area.
1. Shrinking feature size.
Digital has come to 90nm, while analog doesn’t scale that fast and has a gap in process technology with digital.
My view: analog feature may require a certain transistor size, which mean u can not keep scaling down the device while only maintain the W/L ratio.
A simple example is that the flicker noise of a MOS transitory is inversely proportional to W*L, so most Opamp have a pretty large PMOS input pair. (of course u wanna a decent gain as well)
2 Low power
Not like digital, power consumption due to biasing DC current is the dominative portion for analog circuits.
My view: As switching factor is no longer a metric u can play tricks, low power analog design means low-supply-voltage in most cases. Clock gating/sleep mode is useless coz biasing is always there no mater u have clock or not. And low Vth is desired, leakage current is not a big deal, unless for those transistors used as switches.
Ultra-low-power circuits which operate in sub-threshold region can only provide limited speed. (most r current mode)
3. Adaptive architecture
Parameters change dynamically according to the characteristics of incoming signal, is highly desirable in many applications.
My view: Programmable device give digital great adaptive/reconfigure ability, while trade-off for hardware redundancy. Adaptive architectures are not widely used in analog circuits
FPAA seems not to be a trend, maybe just because analog circuits, by nature, are application-specific, or it can’t afford the overhead.
4. Integrated ability
Highly depends on process.
My view: Voltage mode circuits generally require large capacitors, thus double-poly process. RF/Power circuits may need ultra-large capacitors and inductors, off-chip become the only option in that case.
Current-mode circuits have many limitations on performance.
Real integration of mixed-signal system-on-a-chip may not be economically wise.
Those products (so called “mixed-signal SoC”) from industry are actually system-in-package, i.e. many small dies in one package.
5. Die or not.
Not until human being can digitalize themselves.
Any comments or correction or proposals r welcome
Sorry for my bad expression.
Seems to me that quite a few ppl on this board r doing analog IC design or relative stuff.
Let us share and discuss some idea and prospective in the area.
1. Shrinking feature size.
Digital has come to 90nm, while analog doesn’t scale that fast and has a gap in process technology with digital.
My view: analog feature may require a certain transistor size, which mean u can not keep scaling down the device while only maintain the W/L ratio.
A simple example is that the flicker noise of a MOS transitory is inversely proportional to W*L, so most Opamp have a pretty large PMOS input pair. (of course u wanna a decent gain as well)
2 Low power
Not like digital, power consumption due to biasing DC current is the dominative portion for analog circuits.
My view: As switching factor is no longer a metric u can play tricks, low power analog design means low-supply-voltage in most cases. Clock gating/sleep mode is useless coz biasing is always there no mater u have clock or not. And low Vth is desired, leakage current is not a big deal, unless for those transistors used as switches.
Ultra-low-power circuits which operate in sub-threshold region can only provide limited speed. (most r current mode)
3. Adaptive architecture
Parameters change dynamically according to the characteristics of incoming signal, is highly desirable in many applications.
My view: Programmable device give digital great adaptive/reconfigure ability, while trade-off for hardware redundancy. Adaptive architectures are not widely used in analog circuits
FPAA seems not to be a trend, maybe just because analog circuits, by nature, are application-specific, or it can’t afford the overhead.
4. Integrated ability
Highly depends on process.
My view: Voltage mode circuits generally require large capacitors, thus double-poly process. RF/Power circuits may need ultra-large capacitors and inductors, off-chip become the only option in that case.
Current-mode circuits have many limitations on performance.
Real integration of mixed-signal system-on-a-chip may not be economically wise.
Those products (so called “mixed-signal SoC”) from industry are actually system-in-package, i.e. many small dies in one package.
5. Die or not.
Not until human being can digitalize themselves.
Any comments or correction or proposals r welcome
Sorry for my bad expression.
