I have read a few articles, about possibility developing analog computers.Can anyone explain me what difference they will have this computers with modern digital computers compared.Because I don't have enough experience, can anyone help me if this computers will use very complex systems inside compared to digital computer and which analog circuits(e.g amplifiers or something else) may playing a decisive role in this architecture develop.
Electronic – Analog computer
analog-computer
Related Solutions
Analog Devices have papers on the subject, e.g. this one on log amps.
That paper links to the AD538:
The AD538 is a monolithic real-time computational circuit which provides precision analog multiplication, division, and exponentiation. The combination of low input and output offset voltages and excellent linearity results in accurate computation over an unusually wide input dynamic range. Laser wafer trimming makes multiplication and division with errors as low as 0.25% of reading possible, while typical output offsets of 100 microV or less add to the overall off-the-shelf performance level. Real-time analog signal processing is further enhanced by the device's 400 kHz bandwidth.
It's important to note those limitations. 400kHz bandwidth is not very high compared to doing the same arithmetic in the digital domain. That's one of the reasons why almost all control systems computation is done in digital; the others are better linearity, noise tolerance, thermal stability and power consumption.
I know basic rise-/fall slew circuits, but I expect this is different.
For a one dimensional signal it's very basic - it's an RC low-pass filter. Here is the transient response to a step change: -
Trace A is the step input and trace B is the output as indicated in the circuit below: -
And, just in case you have any doubt, you can take an analogue RC filter and digitize it as follows: -
So, if your digital algorithm matches the IIR one immediately above then you have the equivalent of an RC filter.
Best Answer
Large scale analog computers have been around for about 100 years in various mechanical and electrical forms and were used widely in gun and range control during WWI and WWII and probably a lot later than that. So I'm not sure where you are getting your information from.
Indeed, when I went to university in the late 80s we used a large analog computer which was a bit like a huge breadboard with jumper cables that let you connect integrators and differentiators and amplifiers in a rats nest of cables to calculate some output based on some other input. A bit like this one.
Heathkit even had a home version...
Do they have advantages over digital?
Well that depends on what you are trying to do.
Digital is obviously better for maintaining the integrity of the data through the computational process and is not affected by noise, offsets, component tolerances etc. However, digital is also granular and functions with a delay in the time domain.
Depending on what you are trying to control, analog systems, which can accept and process any number of signals simultaneously in the time domain, can still outperform digital in some cases.
Mixed Mode Computers:
If you look closely enough though, in reality, every time you capture a sensor signal and condition it to capture peaks, averages, rate of change etc. before finally capturing it with an ADC, you are in fact using an analog computer to do that.
Analog computers are still alive and well and widely used as sub-systems within most digital computer systems right under your nose.
The trick in designing is knowing when to make the transition.