Some general electronic questions

They'll still stink though, given that the input signal overdrives the NPN.

@koraks Ok, I tried LTSpice I agree that it is far better than Falstad, but the UI is very old fashioned and also a bit complicated to use.

Oh The circuit goes shows completely different behaviour....I think the circuit I posted has some components missing....I took it from the Sparkfun Transistor tutorial. They have not mentioned anything about Impedance of the input and speaker in their tutorial.


Yes, that's its main drawback, I admit. Look on the bright side though - I learned to work with LTSpice something like 15 years ago (?) It hasn't changed since, so I haven't had to relearn anything :wink:

The main issue with your sim in Falstad is/was that the circuit was massively overdriven. If you feed a far smaller signal into it, it actually works fairly well (although no sane audio enthusiast would agree with this statement).

You learnt 15 years ago...that means you're pretty experienced. :slightly_smiling_face:

Let me tell you the truth that I'm still in Grade 10 in school. :wink:


Nothing wrong with that; learn much while you're still young. It gets harder as you get older.

I'm back with my questions again....I did some pre-research on Google but some doubts remain because I found it difficult to understand..

  1. What are Flip-flops? Are they some type of Logic-Gate? PLEASE GIVE A FEW EXAMPLES...

  2. What is Switch debouncing?

  3. Does a MOSFET Gate driver boost logic level voltage? Means if we give 5V input, it gives a higher voltage output to turn on a power MOSFET?

  1. Can anyone here explain me about counters?

  2. What's the difference between a Multiplexer and a Shift Register? Suppose I want to control a Seven Segment display/Led Dot Matrix which one should I choose --> 74HC595 Shift Register, Any Multiplexer or some IC like MAX7219 or TM1637 or LM3914/LM3915?


Depends on the specific part. Most MOSFET drivers will indeed behave as Schmitt triggers, but the margins and hysteresis are part-specific.

Yeah. 1, 2, 3, 4...
Look, that's a very generic question. Please make it more specific.
In the meantime: Counter (digital) - Wikipedia

Multiplexer: essentially a multi-way switch. Connects one input to one of several outputs at a time, or vice versa. Multiplexer - Wikipedia
Shift register: converts a serial input to a parallel output or vice versa. Shift register - Wikipedia

Many ways to skin a cat...several options can work. I find a TM1637 to be the easiest solution mostly. It's very pin-economical; just attach it to the I2C bus along with any other stuff that happens to be on it.

Can we move to the doubts? Because the above is all 3 seconds in Google per question, which you say you've done. So what's the more specific question resulting from those searches?

Generally, a MAX7219, at least that is the one with which I am most familiar. TM1637 would be OK too, the 74HC595 is not designed to be a LED driver and only suitable for tediously driving one single 7-segment display if you must.

The LM3914 is a driver for a bar of 10 LEDs.

You might want to download a copy of Don Lancaster's CMOS Cookbook or maybe the TTL Cookbook.

These are now quite old (pretty much pre-microcontroller), and talk mostly about largely obsolete families of chip (4000 series CMOS or 74 series TTL), but they do a really good job of explaining a bunch of the basics of digital logic, including flipflops, counters, and debouncing.

(good references for everyone to have a copy of, IMO.)

@koraks Sorry, I wrote this post before completely researching so my questions were incomplete. I understood most of your answers just a few questions:

  1. Do we need to debounce for using a push switch with Arduino?

Ok, can you tell me the answer regarding to FAN7392

@koraks I was already reading the wiki articles when I writing the previous post (Most wiki articles look very confusing for me at the first glance).

@Paul_B Ok, got it. Do you suggest any other IC that can drive Single Digit 7 segment display?

@westfw Thanks a lot for the links. I'll read them surely.

Another question: What's the frequency of a PWM signal of Arduino UNO? (Means is it fixed or can we vary it)

When we give the statement analogWrite() does it change the frequency or the duty cycle of the output wave?

Well I did say that for one only 7-segment display, a 74HC595 would be OK; you just have to code it (as you do for all the other displays :sunglasses:). You want a couple of 330 Ohm by four SIP resistors (that is, eight pin ones. Aliexpress does not have these!).

That sounds like a very general statement.
A search for "resistor arrays" in yields pages of them.

Just one example:

Generally, yes. Try it without; you'll be annoyed soon. Especially as the switch ages.

See datasheet, but short answer: yes. Somewhat longer answer: depends on what you supply it with, but generally yes.

Typically something in the neighborhood of 500Hz or 950Hz depending on which pin and which setting. Google should give a definitive answer pretty much immediately...

Duty cycle. It's PWM, remember.

Sorry, I was referring to SIP arrays that are practical on a breadboard/ stripboard etc.

Most gate driver chips accept 3.3 or 5V logic inputs and drive the MOSFET at 12V. This is why they take a 12V supply voltage.

If you look at the datasheet it says the range for Vcc is 10V to 20V. It also shows 15V being used in some of the example circuits. 15V is the nominal drive voltage for a lot of IGBTs, a bit higher than power MOSFETs. This chip is aimed at both MOSFET and IGBT driving.

@koraks, @Paul_B , @MarkT Thank you for the answers.

15V is enough for driving some IRF MOSFET if I ever need them.

Didn't know that a switch ages too, I have seen many switches being used for around 10 years... (Those are home AC switches)

I love coding, so I'll try to code a HC595 with seven segment soon.

I was a bit confused between Duty cycle and Frequency but now it's clear.

Thank you & Regards.

Oh, they'll usually keep working. But many become more 'bouncy' over time. They continue to work fine because...engineers debounce their switches! (Actually, back in the early 1990s when digital technology became pervasive and so did cheap and small electronics, you frequently ran into little gadgets with poorly debounced switches. They worked sort of OK when new, but became more and more horrible to use as they aged.)

Hello, I have a doubt- What wire do you use for making connections between components in a perfboard - Bare Copper OR Tinned copper OR Insulated Solid-core hookup wire ? Also Which Gauge wire do you prefer using?

Can I use bare Aluminium wire with a perfboard?

Whatever is closest to my right hand as I'm building stuff. IF I use perfboard. Never do anymore, but used to.

Try soldering to aluminium. You'll be old and grey before you manage it.

Stick to copper. Doesn't matter if it's solid, stranded, etc. etc. Use decent rosin-core solder and keep some flux at hand.

Standard (tin-based) solder will not wet Al at all, and specialized aluminium solder may not wet other metals for all I know. This is why aluminium wire for electrical use is often copper-coated (aka CCA).