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Low voltage design in analog circuit is use for new transistor process?

B

Boki

Jan 1, 1970
0
Hi, All:

Does Low voltage design in analog circuit is use for new transistor process?

I guess it due to analog circuit maybe not decrese power consumtion with
power supply.

Thanks!

Boki.
 
T

Tim Shoppa

Jan 1, 1970
0
Boki said:
Does Low voltage design in analog circuit is use for new transistor process?

I guess it due to analog circuit maybe not decrese power consumtion with
power supply.

"Analog" is a very vague term. Digital systems *are* made from analog
parts so everything is analog.

Even in, say, switching power supplies ("analog" circuits by most definitions)
it is desirable to have small voltage drops across switching components.

Tim.
 
K

Kevin Aylward

Jan 1, 1970
0
Paul said:
I Think what he's trying to ask, is why digital component power
supplies keep dropping, (1.8V and falling) while the fall in analog
supplies is not so dramatic. I wonder if digital supplies will keep
falling though zero, maybe ending up at -5.2V?

Paul Burke

Ok, he could be asking, "Why do analogue designs not use the lower
voltages that are becoming more prevalent in the newer digital designs"

The answer to this, is that is very difficult to get the performance at
low voltages.

For example, a push pull emitter follower will lose two diode drops, say
1.5V, if you want just 1V swing, you would need a 2.5V supply. Rail-rail
designs, using collector outputs, can have stability and bias setting
problems, especially if its cmos, e.g. subthreshold operation often
required. Frequency response is also an issue, as low voltage limits the
ability to use cascodes. Signal to noise and dynamic range is also an
issue. All in all, you don't really want to go below about 5V for an
analogue design.

Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
 
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