Transistor equivalent

audioguru · Nov 22, 2015

Mr Al, the crossover distortion example I posted has the IC with a plus and minus supply and its load connected to 0V therefore neither output transistor is class-A. I said the output transistors were not biased in class-AB like all linear amplifiers, but instead they are biased into class-B without enough conduction to prevent crossover distortion. It was designed that way so that the power is very low.
Of course you can add a resistor to the positive supply or to a negative supply to cause one of the output transistors to be a class-A heater but Spec said in this thread it causes other problems.

I worked with a Korean telephone system using an LM358 with crossover distortion that customers complained about. I fixed it with a load resistor. It was the only circuit I touched that used a lousy old LM358 or LM324.

audioguru · Nov 22, 2015

I checked a TIP35 datasheet that is 41 years old and it says its max current and max dissipation are 1000 times more than on Spec's graph (I cannot click on an item on the graph for its link to open).

spec · Nov 22, 2015

OOPS! will fix. Just a sceen capture so links wont work .... Done

audioguru · Nov 22, 2015

Are those monster sized old power transistors rated at only 125mW?

audioguru · Nov 22, 2015

This thread that is talking about very old parts is like watching a silent movie from the '20ies. It is too bad that people "over there" talk to people "over here".

spec · Nov 22, 2015

audioguru said:
This thread that is talking about very old parts is like watching a silent movie from the '20ies. It is too bad that people "over there" talk to people "over here".

Why watch then?

audioguru · Nov 22, 2015

I know what is going on. Guys "over there" cannot buy common parts that we use and talk about and those guys are hoping that one of us will send him some of our modern parts. It happens often.

spec · Nov 22, 2015

audioguru said:
I know what is going on. Guys "over there" cannot buy common parts that we use and talk about and those guys are hoping that one of us will send him some of our modern parts. It happens often.

Oh! I see- lack off experience on my behalf shows here.

KeepItSimpleStupid · Nov 22, 2015

spc:

ETO used to support tables. I just reported it as a bug. I think I may have used the function a few times here. When it works, you can use an external site like https://www.teamopolis.com/tools/bbcode-table-generator.aspx to generate your table.

Otherwise, the closest you can get is to use [code] [/code]tags

Code:

       header 1    Header 2
Row 1     5          7
Row 2     9         10

When composing, set the font to a fixed proportion, like "Courier New" between the tags. You have to use Preview to preview the results.

spec · Nov 22, 2015

Thks for that Keep. I was wondering why no tables. I put a formula into Latex editor but could find no way to get the displayed equation into the post

KeepItSimpleStupid · Nov 22, 2015

I find something like this: https://www.codecogs.com/latex/eqneditor.php to be a better Latex editor.

[latex]\int_{1}^{t}xdt[/latex]

You just have to copy the latex Code and add the [latex][/latex] surrounding tags.

spec · Nov 22, 2015

You're a star!

spec · Nov 22, 2015

KeepItSimpleStupid said:
The self book is a nice book. There aren't a lot of amplifier design books. I'd like to find one on FET current sources, electrometer amps and nulling input bias currents.

re electrometer amps, expect you have seen this:
https://www.ti.com/lit/ds/symlink/lmc6001.pdf

MrAl · Nov 23, 2015

spec said:
You're a star!

Hi,

That's a great idea, but i thought i would mention another idea that ensures that the post will always be at least somewhat readable. This comes into play because often the Latex site code break down or just doesnt work due to a forum upgrade, and sometimes it takes quite a while to be fixed. I mention this on other sites too now because it has happened on EVERY site i have ever replied in.

The idea is very simple, and that is to provide some redundant information in the form of pure text. This takes a little extra time but not much and but provides two important advantages:
1. If the Latex code breaks down the message is still fully readable.
2. The reader can copy and paste the equation(s) right into their home math software.

To illustrate, a simple example:

[Latex]
Y = \int \mathrm{y}\left( t\right) dt
[/Latex]

Y=integral(y(t),t)

As you can see in the attachement, the latex code worked in the Latex editor, but not in the forum. If it were not for that pure text line, you would not be able to read that equation at all unless you were willing to decipher the latex code itself manually.

spec · Nov 23, 2015

Thanks a lot MrAl- you're a star too!

Nikolai Petrenko · Nov 23, 2015

I will buy that components in the next year's summer holiday, because 2 reasons:
- I will use my parents' account to pay for that components under they permission
- This year I have to pass two very important exams
I also want you post circuits:
- 2N3055-2955 amp. with 40w into 4ohm and 8ohm (because I don't know what types of subwoofer I will buy)
- other discrete transistors amps (that has good sound qualiy) with 20w into 4ohm and 8ohm (that amps will drive satellite speakers)
- I also want to know power supply requirements of above circuit
And finish, thank a lot peoples that help me!

audioguru · Nov 23, 2015

If you want to save money then the speaker impedance must be determined first:
1) The amplifier driving a 4 ohm speaker needs more current from the power supply but the power supply voltage for it can be less than the amplifier driving an 8 ohm speaker.
2) The amplifier driving an 8 ohm speaker needs more voltage from the power supply but the power supply current for it can be less than the amplifier driving a 4 ohm speaker.

Do you know the simple calculations for the transformer voltage and current? Maybe a higher voltage lower current transformer is available and costs less than a higher current lower voltage transformer that might not be available.

MrAl · Nov 23, 2015

KeepItSimpleStupid said:
I find something like this: https://www.codecogs.com/latex/eqneditor.php to be a better Latex editor.

[latex]\int_{1}^{t}xdt[/latex]

You just have to copy the latex Code and add the [latex][/latex] surrounding tags.

spec said:
Thanks a lot MrAl- you're a star too!

Well that's nice of you to say.

I just looked at KISS's code and saw that his example worked, so i redid mine:

Latex:
[latex]\int_{0}^{T}y(t)\, dt[/latex]

text:
integral[0 to T] y(t) dt

so it should work now, but if it breaks we would also have the text too.
If the text is entered in a more program friendly form, they can copy and paste it:
integrate(y(t),t,0,T)

whereas with the Latex they cant do that. This is even more useful when the equation is much larger like 50 characters long.

Have fun with it

spec · Nov 23, 2015

I will be an expert soon!

MrAl · Nov 23, 2015

spec said:
I will be an expert soon!

Hi,

From your posts i assumed you were already

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