some basic questions on eletronics

[arava prakash]

1.which one is dangerous to human ?
AC (or) DC.
2.mobility of electron is greater than hole. why?
3.what is difference between analog ic design and digital ic design ?
Is one is a part of another

 

[arava prakash]

some basic doubts on electronics

1.is hole is exist in nature?
(because commonly refer ed as hole is a non-existence of electron)

 

[betwixt]

1. Both are dangerous if the current flowing through the body is high enough.
2. Not sure that is correct.
3. Analog IC is designed to work with any voltage within it's operating range. Digital ICs are designed to work at one of two voltage ranges, called "high" and "low". In other words digital ICs are optimized for binary operation. The silicon fabrication process is similar between the two, it is the functionality of the circuit that is different.

Brian.

 

[tarun0xe]

1.which one is dangerous to human ?
AC (or) DC.
2.mobility of electron is greater than hole. why?
3.what is difference between analog ic design and digital ic design ?
Is one is a part of another

your 1st and 3rd questions have been already answered by betwixt, about 2nd question and also your other question about existence of holes you have to visualize the actual structure of semiconductor(especially the most commonly used i.e silicon)...... read few points given below.

1.Whenever electron leaves an atom it leaves a positive charge of 1 unit on its parents atom, that we usually call hole as it can be also observed as a vacancy being created where there was that electron earlier. For understanding purpose, assume that electron has gone towards left side in x-axis. The vacancy created may be filled by some other electron(from some nearby atom) soon as electron leaves or after sometime. So now an original atom gets neutralized but positive charge(hole) appears on new atom from which the electron jumped to fill that earlier hole. We can visualize this as a net negative charge has gone to left side and corresponding to that some positive charge(hole) has moved to opposite i.e right side(why hole comes only from opposite side, that I'll explain in next point).

2. As there is a net flow of charge with respect to time(current flow) through the semiconductor device we are sure that electrons coming to fill holes comes from side opposite to which our earlier electron has gone, otherwise an electron gone to one side and another electron coming from same side would not have created a net flow of charge and thus no current would be flowing through our device but since a net current is flowing the opposite is true, i.e electrons and holes flow towards opposite sides.

3. Mobility is usually expressed in cm^2/(V.s) and represents how easily a charged particle can flow through semiconductor device. It is affected by the collisions the charged particle undergo while its path. As we see, holes(a positive charge) just comes to fill the position of electron it seems as if mobility for both electrons and holes, should be same for same material but it is off course different with electrons having much higher 1350cm^2/(V.s) against holes 480cm^2/(V.s) for intrinsic silicon. The main reason is, holes don't come instantly to fill electrons position. They may or may not fill that vacancy soon it is created which again depends on a number of conditions. So the mobility of electrons is higher than holes.

 

[D.A.(Tony)Stewart]

1. human muscles work by a pulse train from synapse via chemical path so either AC or DC will contract muscles and if strong enough thru heart will stop it.

2. - mobility of an electron is like energy to move a bucket in a water brigade.. it only has to move 1 bucket, whereas if everyone has a bucket except one person, the mobility is all the buckets moving with the hole being the person without a bucket.

so it is like electron and hole mobility.

3. All digital designs have analog characteristics except the threshold is fixed and levels are saturated to binary levels with an effective series resistance output and input capacitance. But the threshold for TTL is 2 diode or PN drops or 1.3V while CMOS is often Vcc/2 or 2 PN drops like CMOS RS-232 receivers.

Whereas analog design is usually operating in the non-saturated mode or LINEAR mode.

But in fact most digital unbuffered CMOS gates have designed analog gain of 10 or buffered gain of 3 stages for an inverted output or a gain of 1000 so feedback and input resistors ( usually > 10k) to convert the digital gate into a linear amplifier like a single ended (-) op-amp, and can be used up to the max open loop gain, when one is creative, such as a sensor amplifier with AC coupling or DC bridge biasing to Vcc/2.