Hello everyone,

My question is about designing electronic circuit to achieve best performance and avoid burning of ICs. well i know how to connect simple BJTs, MOSFETs, opamps, etc .. but i need to understand how do someone realize that he needs a capacitor to filter, or need a RC circuit, or even needs a resistor, capacitor or a diode somewhere in the circuit for better performance.

What are the knowledge or references needed for applying this ? and do simulating programs help in that ?

Once, I asked a question about Bootstrap capacitors and SGT explained its function for me and even show me a simulation using LTspice for a mosfet with bootstrap and a mosfet without it and the difference in performance.
This is the thread: http://forum.allaboutcircuits.com/showthread.php?t=55599

So again, how would i know that i needed a bootstrap capacitor to avoid heat dissipation as explained in the above thread ? how would i know these information in designing any circuit using triac, mosfet, bjt or anything ?

Thanks in advance.

 

Hello everyone,

My question is about designing electronic circuit to achieve best performance and avoid burning of ICs. //////

So again, how would i know that i needed a bootstrap capacitor to avoid heat dissipation as explained in the above thread ? how would i know these information in designing any circuit using triac, mosfet, bjt or anything ?

Thanks in advance.

First: you have to be able to define or describe what it is you are trying to design.

 

Education and experience. Both are necessary. When you have both, looking at the design will lead you to investigate weaknesses and know what to do about them.

 

but i need to understand how do someone realize that he needs a capacitor to filter, or need a RC circuit, or even needs a resistor, capacitor or a diode somewhere in the circuit for better performance.

....better performance ? What does this mean?

There is a general rule in electronics: Improvement of one particular parameter is connected with degradation of another parameter that perhaps is equally important.
As a consequence, each good design is a trade-off between several (mostly conflicting) requirements:
Performance (main task), power dissipation, reliability, weight, cost, input/output charcteristics, sensitivity to tolerances and environment, tunability, frequency range,....

The fulfillment of the above describes the task of a good engineer.

 

okay, performance can be translated to safety and long life time for the IC.
I stated above the Mosfet example, where it could work normally without a bootstrap capacitor but will give high power dissipation and will effect on its life time and performance. but if i used a bootstrap capacitor ( and that's my question, how would i know that ? ) the power dissipation will be very low and the IC won't overheat.

well that question came to my mind while i was searching for a zero cross reference circuit, where i found several designs.

http://forum.allaboutcircuits.com/blog.php?b=506
http://forum.allaboutcircuits.com/attachment.php?attachmentid=62956&d=1388222388
http://forum.allaboutcircuits.com/attachment.php?attachmentid=22876&d=1285173066
http://forum.allaboutcircuits.com/attachment.php?attachmentid=22888&d=1285226243
http://forum.allaboutcircuits.com/attachment.php?attachmentid=22889&d=1285233856

well the one i used was the first one and it works fine - of course i didn't use an oscilloscope to be sure - but it worked fine.

afterwards i found a topic about safe pwm dimmer
http://www.instructables.com/id/safe-and-simple-AC-PWM-Dimmer-for-arduino-Raspberr/

so that's why i was asking my question, why won't i just use the first link and connect the AC wave to optocoupler and take a pulse every rising edge of the AC ?
why was the last link from instructables called "safe" ?

 

This is another example for a zero cross reference using op amp not bjt,
http://www.instructables.com/id/AC-Lamp-Dimmer-Using-TRIAC-and-PIC16F877A/

or this
https://forum.allaboutcircuits.com/showpost.php?p=235099&postcount=3