[Editor's Note] To effectively use LTspice, an analog circuit design tool, one needs an intuitive understanding of analog circuits beyond basic usage. In this context, e4ds news has prepared a training program designed to help students develop design skills by simulating real-world circuits such as amplifiers, filters, switching power supplies, and ADCs, and to strengthen practical capabilities through examples connected to industrial sites, such as flyback converters. Accordingly, we met with Professor Im Seung-chan, who will be in charge of this training, to hear about the lecture content as well as the continued importance of analog technology and the value of collaboration among engineers.


■ Please give a brief introduction to the content of this LTspice Intensive Master Class.

LTspice is one of the excellent analog circuit design tools.

It allows us to simulate the operation of complex circuits, just as we observe waveforms with an oscilloscope or view frequency response screens with a spectrum analyzer, without having to solve Maxwell's equations of electromagnetics or systems of differential equations of circuits.

On the other hand, no matter how excellent a tool is, one must have an intuitive understanding of the basic behavior of the circuit to be simulated.

This training is designed to go beyond simply mastering the use of LTspice and to help you gain an intuitive understanding of the various circuits we encounter, namely amplifiers, active filters, mixers, linear and switching regulators, ADCs, and DACs.

SPICE, a text-based circuit simulator, is the most widely used analog circuit simulator since it was developed at UC Berkeley and commercialized in the early 1980s.

In addition to Analog Devices' LTspice, simulators based on SPICE include Cadence's PSPICE and National Instruments' Multisim.

Among these, LTspice can be downloaded and used for free, and in addition to Analog Devices products It can be called the ultimate analog simulator because it also allows the use of libraries for IC components from Linear Technology and Maxim, which were acquired by this company.

I am curious about the most common difficulties practitioners face while learning LTspice and how these can be resolved in this lecture.

While it is true that powerful analog circuit simulators provide convenience to circuit design engineers, they do not suggest how to change component values and parameters if the simulation results are unsatisfactory.

Ultimately, LTspice is just a tool, and designing a great circuit is the designer's job.

This training will proceed by reviewing key concepts from the circuit design and electronic circuits courses you studied in university to help you gain an intuitive understanding of various basic circuits.

■ The curriculum includes a practical exercise on an LT8306-based flyback converter. Is there a particular reason for selecting this example?

The biggest advantage of a flyback converter is that it isolates the power supply side from the load side, that is, electrically separates them.

By doing this, the ground loop is isolated, which can reduce EMI noise, protect sensitive components from electrical shocks or power surges, and prevent casualties.

Of course, optocouplers can be used for circuit isolation, but this method is disadvantageous in terms of response speed, linearity, temperature variation, and operating range.

Flyback converters also offer various functional advantages, such as the ability to perform both Buck (step-down) and Boost (step-up) operations and obtain multiple outputs, and are also inexpensive. />
It also provides an educational benefit of learning what an Air Gap Transformer is, what its advantages are, and how Faraday's law of induction is applied.

■ What is the greatest learning benefit students will gain from BJT amplifier design or OP AMP filter practice?

When learning about the design of BJT or FET small-signal amplifiers in a university electronic circuits course, we went through a complex process of calculating the DC current through DC analysis, determining small-signal parameters using the results, and then performing small-signal analysis.

On the other hand, using LTspice allows you to experience the convenience of obtaining the transient response and frequency response at once.

In principle, it is possible to implement higher-order filters using OPAMP active filters, but because the formulas become too complex, there are likely many cases where students stop at solving up to second-order filters in university.

In this training, you will realize the power of the simulator while designing a 4th-order narrow bandpass filter using a single IC (LT 1568).

■ If you were to introduce examples of connections to actual industrial sites in the application circuit simulation (ADC, regulator, switching power supply, etc.) part,

This course covers how to measure key parameters such as ripple voltage and efficiency during regulator simulation using LTspice, thereby minimizing trial and error during power supply design.

In addition, it is possible to determine how the ripple voltage increases or decreases as the load conditions are changed.

Even if a circuit is designed and manufactured without any functional issues, there are many cases where users struggle with EMI noise generated by switching power supplies.

Analog DivideWe also plan to introduce the principle by which S's EMI-Silent switching regulators do not generate switching noise.

■ What do you think is the first 'practical sense' that field engineers need to acquire through LTspice?

There are cases where the LTspice simulation results differ from the actual implemented results.

This is not a defect in LTspice, but occurs when the part model used during simulation differs from the characteristics of the actual part used.

In such cases, a deep understanding of the parts we use is necessary.

Therefore, even if you enjoy the convenience of LTspice, consistent study of circuit theory, electronic circuits, and thorough reading of component datasheets is necessary.

Analog circuit design engineers are generally highly focused but tend to be stingy with collaboration or the transfer of know-how.

I believe that if these barriers are removed, individuals and organizations can achieve more.

There is one more thing I would like to mention.

There is a maxim that says, “Do not reinvent the wheel.”

It means there is no need to waste time and effort redeveloping good things that already exist in this world.

It is highly likely that the circuit you intend to design is not something you are making for the first time in this world.

Also, it is highly likely that the problems you encounter during the design process are not the first of their kind.

If you find good circuits through the LTspice demo circuit library and engage in good communication through community activities, analog circuit development work will become a more relaxed and enjoyable time. />
■ Finally, please say a few words to the readers of e4ds.

Seeing the announcement for LTspice training, an analog circuit simulation tool, on the e4ds webinar guide page, some people may wonder why there is any mention of analog in a world where everything is connected by digital and AI.

On the other hand, I would like to point out that digital technology has not yet been able to replace applications requiring high frequency ranges, high precision, and high-speed response in wireless communication.

I also asked the artificial intelligence.

I asked if AI could replace analog design work. The AI's answer was No.

It is said that the reason is that the rate at which analog design know-how is shared via the internet is lower compared to digital, making it difficult to collect data for AI to learn.

Therefore, analog is an area that humans, not AI, must continue to handle.

Analog circuit technology is also necessary for developing core sensors for physical AI, ultra-small precision motor drive circuits, and ultra-small high-efficiency power supplies.

In other words, it is a technology closely related to the AI world that will come in the future.