Diode is in!

Yes ! One more non-linear element in SimOhm ! SimOhm has recently launched a new non-linear element named diode, familiar with most of you, at least electrical engineers or physicists. However this diode will make you able to create more advanced circuits, and view their transient response.

Before going into technical details, lets state some important things a diode can do. Do you know that your laptop or mobile charger works on direct current (DC), which means that we have a stable constant current of zero frequency. But the power provided from the electrical grid in our countries provide alternating current (AC) only, so how to change this alternating current to a dc current? In that case we will need a rectifier. A rectifier is a name given to a big box, which can be found in every single building in the power or telephone room place in that building. This rectifier has a rectifier circuit. This circuit as shown in the simulation below has an alternating source, a diode and a resistor connected in series. This diode has the property of making current flow in one direction only. The diode has two junctions (ends), cathode (the n-doped layer which has the negative charge -electrons-) and anode (the p-doped layer which has the positive charge -antimatter or protons-). In a circuit current flows from positive to negative, so this means that current in a semiconductor flows from the negative to positive (from n to p) and can never move from positive to negative, and this property makes the diode a unique electronic semiconductor component which makes current flow in one direction only. This gives rise to many applications where a diode can be used in, such as the conversion from alternating to direct current explained above. The diode is also used in envelope detection circuits which are used in amplitude modulation (AM) in radio communication systems and several other applications. Diode as also used in npn or pnp BJT or MOSFET type transistors, which are used as electronic switches and they also have a wide scope of applications which might be explained later in another post.

Now lets see how can we play in this device and create several applications. As stated above, the diode can be used in rectifier circuits. But in simulations, we just state several assumptions, and model our system using accurate parameters. To create a diode in SimOhm, every diode has a threshold voltage. This voltage changes with the temperature surrounding the diode. An increase in temperature, increases the voltage across the diode and viceversa. Coming back to threshold voltage, this voltage is the minimum voltage required for a diode to operate. You can vary the threshold voltage but for our modeled diode, we have a threshold voltage of 0.01V. In addition, you can vary the diode forward and reverse resistances (forward resistant is the resistance a diode should have when the voltage is above the threshold voltage -and this should be as small as possible o.1-; whereas, reverse resistance is the resistance a diode should have when it the voltage across it is less than the threshold voltage -and this should be as maximum as possible, infinity-).

Play the simulation and see how the alternating voltage operating in the positive and negative region gets to operate only in the positive region, by taking the output voltage on the capacitor (note that in practice, conversion from AC to DC requires a rectifier and a stabilizer circuit in order to have a constant output voltage):

Increase the simulation speed for faster results.

And below is a clipper circuit:

Confident enough?

Now go ahead and create design your own simulation @ http://www.siminsights.com

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SimOhm

Electrical Simulations? What are electrical simulations?
Simulations in general allow us to take any physical real time system or device and model it using mathematical models, in order to study its behavior changing any of the characteristics that may influence the way it behaves.

But why do we want to change the characteristics, why do we want to study its behavior, why do we want to simulate?
We study the behaviour due to many reasons, one of them is to be able to know how does our device behave under certain circumstances, so if we place a diode at a certain temperature, how will it behave? What if the temperature increases, will electrons move faster in a circuit leading to faster results in a shorter time? Or will it have no effect at all? What if I connect a resistor in series with a capacitor, how will the voltage output on the resistor will change with time? What if I take the voltage output on the capacitor itself, can this response be used in any nowadays device? All these questions may be answered by engineers and not technicians* only through simulations when they will be able to change different circuital parameters without needing to implement this practically.

Another reason is efficiency. How efficient simulations would be? I would consider them 99% efficient, since 1% lies to the time one spends doing the simulations, although I would give it a 100%, so if someone wants to build a circuit in real life and test its transient response, I bet he would not get it right unless after repeating it several times. So using electrical simulations, you can design your own circuit, test its response with time, and if it worked as per your need for a project or whatever, you can go ahead and implement it practically. So you wont spend time and money fixing several circuits with several components and burning several components due to unexpected high current or whatever.

*Next time we will talk about the difference between an engineer and a technician and how it is related to our topic.

Collaborative circuit simulations

Introducing SimOhm - a web-based collaborative circuit simulation tool. Build your circuits and share with others. Following is an example circuit. Feel free to play with  it. To build your own circuits, just login to www.siminsights.com and start inventing.