Category Archives: Other Cources

LINEAR VERSUS SWICTHING POWER SUPPLIES

Switching and linear regulator use fundamentally different techniques to produce a regulated output voltage from an unregulated input.Each technique have advantages and disadvantages.So the application will determine will determine the moist suitable choice.

Linear power supplies can step-down an input voltage to produce a lower output voltage.This is done by operating a bipolar transistor or MOSFET pass unit in its linear operating mode.

Operating in this mode means that there is always a headroom voltage.Vdrop,between the input and the output.The linear regulators are 35 to 65 percent efficient and linear are cost-effective in step-down applications.

A low drop-out (LDO) regulator uses an improved output stage that can reduce VDROP to considerably less than 1.0V.This increases the efficiency and allow the linear regulator to be used in higher power applications.Designing with a linear regulator is simple and cheap,requiring few external components.A linear design is quieter than switcher since there is no high-frequency switching noise.

Switching power supplies operate by rapidly switching the pass units between two efficient operating states that is CUT OFF,where there is a high voltage across the pass unit but no current flow.

And the second is SATURATION,where there is high current the pass unit but at very small voltage drop.Switching power supplies are much more efficient,ranging from 65 to 95 percent.

The downside of a switching design is that it is considerably more complex.In addition,the output voltage contains switching noise,which is must be removed for many applications.

Although there are clear differences between linear and switching regulators,many applications require both types to be used.For examples,a switching regulator may provide the initial regulation,and then a linear regulator may provide post-regulation for a noise-sensitive part of the design,such as a sensor interface circuit.

What is Nixies

Gas disharge plasma displays are the most well known type of alphanumeric displays.Their operation is based on the emission of light in a cold cathode gas filled tube under breaking down condition.These cold cathode numerical indicators are called Nixies.(Numicators and Numbertrons).

The Nixie tube is a numeric indicators based on glow disharge in cold cathode gas filled tubes.It is essenntially a multicathode tube filled with a gas such as Neon and having a single anode as shown in fig.

Each of the cathodes is made of a thin wire and is shaped in the form of characters to be displayed,for example,numerals 0 to 9.The anode is also in the form of a thin frame.In its normal operation ,the anode is returned to positive supply through a suitable current limiting resistor,the value of the supply being greater than the worst-case breakdown voltage of the gas within the tube.The gas in the vicinity of the appropriate cathode glows when the cathode is switched to ground potential.

Since 10 cathodes have to be associated with a single anode inside the glass bulb,they have necessarily to be stacked in differnt planes. This requires different voltages for differnt cathodes to enable the glow discharge.

Many Nixie tubes also possess dot-cathodes either on the left or right of the character to serve as decimal points.

Firewalls

A firewall is a system that enforces an access control policey between two networks-such as your private LAN & the unsafe,public internet.The firewall determines which inside service can be accessed from the outside & vice-versa.The actual means by which this is accomplished varies widely,but in principal,the firewall can be thought of as a pair of mechanism:one to block traffic & one to permit traffic.A firewall is more than the locked front door to your network it’s your security guard as well.

Basic Purpose of a Firewall

Basically,a firewall does three things to protect the network:

  • It blocks incoming data that might contain a hacker attack.
  • It hides information about the network by making it seem that all outgoing traffic originates from the firewall rather than the network,this is called network address translation.
  • It screens outgoing traffic to limit internet use or access to remote sites.