Peak Detector

With little modifications basic precision rectifier can be used also for detecting peak levels of signal. In the following circuit a capacitor keeps the peak voltage level of signal and switch can be used for resetting detected level.



Precision rectifier:Part-1

The  precision rectifier, which is also known as a super diode, is a configuration obtained with an operational amplifier in order to have a circuit behaving like an ideal diode or rectifier. It can be useful for high-precision signal processing

 Basic Circuit



 This circuit has the benefit that the op-amp never goes in saturation, so the only thing affecting its frequency response is the amplification and the gain-bandwidth product.

Similar circuitry can be used to create a precision full-wave rectifier circuit.

 The basic circuit implementing such a feature is shown on the right, where RL can be any load. When the input voltage is negative, there is a negative voltage on the diode, too, so it works like an open circuit, there is no current in the load and the output voltage is zero.


When the input is positive, it is amplified by the operational amplifier and it turns the diode on. There is current in the load and, because of the feedback, the output voltage is equal to the input.


In fact the threshold of the super diode is not actually zero, as it should be for an ideal one, but it equals the threshold of the normal diode divided by the gain of the operational amplifier, that is almost zero.


 This basic configuration has a problem so it is not commonly used: when the input becomes (even slightly) negative, the output of the operational amplifier can easily become greater than the voltage supplied to the op-amp, thus causing saturation. Then, if the input becomes positive again, the op-amp has to get out of the saturation to amplify again. This change takes some time, and this greatly reduces the frequency response of the circuit. 

    Improved Circuit


In this case, when the input is greater than zero, D1 is OFF and D2 is ON, so the output is zero, because one side R2 is connected to the virtual ground, and there is no current through it. When the input is less than zero, D1 is ON and D2 is OFF, and the output is like the input with an amplification of ? R2 / R1. Its transfer characteristic is the following:


This circuit has the benefit that the op-amp never goes in saturation, so the only thing affecting its frequency response is the amplification and the gain-bandwidth product.

Similar circuitry can be used to create a precision full-wave rectifier circuit.

Phase locked loop




DPLL Image
DPLL Image

o       The PLL uses phase lock to perform its intended function.

o       Before phase lock can occurs it must have frequency lock.

o       After frequency lock has occurred, the phase comparator produces an output voltage that is proportional to the difference in the phase between the VCO output frequency and the external input frequency.

o       When there is no external input signal or when the feedback loop is open, the VCO operates at a preset frequency called its natural or free-running frequency (fn) .

o       The natural frequency is the VCO’s output frequency when the PLL is not lock.


Short for phase-locked loop, an electronic circuit that controls an oscillator so that it maintains a constant phase angle (i.e., lock) on the frequency of an input, or reference, signal. A PLL ensures that a communication signal is locked on a specific frequency and can also be used to generate, modulate and demodulate a signal and divide a frequency.

PLL is used often in wireless communications where the oscillator is usually at the receiver and the input signal is extracted from the signal received from the remote transmitter.

Digital PLL (DPLL)


Digital PLLs are a type of PLL used to sychronize digital signals. While DPLLs input and outputs are typically all digital, they do have internal functions which are dependent on analog signals. There are four basic components of a DPLL.



Educational Webportals

Having a webportal is the best way to serve prople if you are associated with a corporate ot Institution or may be freelancer  serving society in any way. Webportals are not just staic websites ,they are dynamic in nature and provides the best way to satify the requirements of  each single user of the system(Ideally).This may be a total interactive platform between a user and others associated with this.
What are the advantages if I have a webportal for my institutions/Corporate sector?
If you have a webportal then no matter how far the memebers and peoples who are attached with
your Institutions/Company , they will be always in touch through the  services provided by the webportals.
From educational point of view in can be said that the webportal can be an easy way and service to help all students by helping them involved in a total way from knowledge sharing to direct teacher interaction and also from learning to implementation by deep sharing of informations and knowledge between teachers ,friends, seniors,juniors and others.
IS there any other advantage

There may be other indirect advantage.
For eaxmple when you have an active webportal online ,that means your site activity and portal is viewable by all the world.So people residing outside the country may come accross your portal activity and may
be influenced enough to join the institution as a foreigner candidate(Provided you have the foreign student intake capability according to your country rules).
So in brief
having a webportal means  lots of students teachers attached with it.(Please note I am talking about educational webportals) So have fully functional student-teacher community active round the clock(Ideally).One such kind of organization that can give these services at FREE is

Ragging : What the real problem is : Part I

We failed to save the student from being ragged to ultimate death of 1st year student of Hamachal Pradesh.
Stdunet  of Dehradun’s school can’t save his ears from raggers and there are many more results all around the INDIA.
Though the Govt. has taken very strict steps in this matter but still the incidences are still occuring either in big scale or in small scale.

Whenever a student takes admission to new college the challenge is to adopt the new structure (educational) and environment of the college.Another big challenge is wining over the fear called Ragging.
The untold truth is that  if you pass the ragging test conducted by your seniors then you will stay peacefully during test of your studey else …..may have a big problem.

Most of the parents stay in anxiety about how to cope with this problem,how to mentally prepare their sons/daughters about ragging,where to go for justice if students get ragged.Most of the parents are in dark in these matters.

Whenever a person’s own son/daughter become a victim of ragging then everything becomes so much dishevelled that people can’t think where to go ,whoose suggession  is to take or compromise with the issue for the future of the student (as sometimes college  also wants to conceal the matter).Students also lost their self confidance as wel a s get disappointed.

So Blog readers do you have any suggessions in this matter ,then write your comment.

Part II  Coming Soon……

In The next part I will discuss about the self confidenace building for facing the ragging..

If  Anybbody has any good ideas of how to protect ragging and how to cope with ragging activities,their comments are welcome to this post.