# coupling

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#### moolameela

##### New Member
hello everyone i'd like to understand the difference between direct - capacitive - resistive coupling how will the output look like
i.e : i need to understand the i/p & o/p waveforms are in phase or out of phase and so on
plz i need help as soon as possible

#### colin55

##### Well-Known Member
You can find the answers to all these questions on the web.
It is pointless us re-inventing the wheel and producing an encyclopaedia for you when all the things are already available. Just go to wikipedia.

#### moolameela

##### New Member
i don't need any encyclopedias
and my point was clear i need to see the o/p wave form of each type as on the oscilloscope
and if u find it on wikipedia just pass the link to me

#### crutschow

##### Well-Known Member
Since you appear to be search challenged, Google "AC coupling" or "RC coupling" or "Capacitive coupling".

#### colin55

##### Well-Known Member
I don't need any encyclopedias
That is exactly what you are asking for! Imagine the number of waveforms that would need to be produced to provide you with the results for: "direct - capacitive - resistive coupling and how the output will appear" for all the range of frequencies and input waveforms. I can already see 200++ circuits, just to cover this request. There are 9 different direct couplings to start with. Then there are more than 10 different frequencies . . . the list goes on. How many combinations and permutations do you want to cover?

#### colin55

##### Well-Known Member
Boncuk

Here is something you didn't agree with a while ago:

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I notice the circuit you have provided on your more-recent post is entirely different to the circuit I criticised last year.
You have obviously learnt that a 555 will not turn off a transistor and have modified the circuit accordingly.
None of my students would try to get away with sneaking in a modified circuit and saying “see the circuit DID work.”
Nice try but you will have to get up earlier than that to fool me.
This has obviously been infuriating you for the past 4 months. But you have learnt a lot.

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#### moolameela

##### New Member
ok i didn't get that at first

#### Attachments

• direct coupling stage 1.pdf
443.4 KB · Views: 121
• capacitive.pdf
814.5 KB · Views: 156

#### colin55

##### Well-Known Member
To start with, direct coupling stage 1.pdf involves two transistors in a circuit that is rarely, if ever, used in practice.
It is absolutely pointless learning about two stages that you will NEVER come across. And the same applies to: capacitive.pdf

#### moolameela

##### New Member
it's obligatory unfortunately
but what about cap and direct coupling stages does their output achieve the goal or what
i.e: when u say inverter u find o/p signal inverted whatever how it looks , the same thing i need to know about these two circuits

#### colin55

##### Well-Known Member
it's obligatory unfortunately
but what about cap and direct coupling stages does their output achieve the goal or what
i.e: when u say inverter u find o/p signal inverted whatever how it looks , the same thing i need to know about these two circuits

It sounds like you are getting us to answer a homework problem from a course you are trying to squeeze your way through.
This is the sort of idiotic question produced by lecturers.
It gets you nowhere. Even if it is complex and you spend a lot of time on it, the effort is wasted.
The second stage is up-side-down and you need to re-draw it so that at least you are working on a circuit that has a conventional layout.
We are not here to untangle things for you.
And secondly, you need to express yourself clearly in English so that we can understand what you are trying to say.

#### Boncuk

##### New Member
Boncuk

I notice the circuit you have provided on your more-recent post is entirely different to the circuit I criticised last year.
You have obviously learnt that a 555 will not turn off a transistor and have modified the circuit accordingly.
None of my students would try to get away with sneaking in a modified circuit and saying “see the circuit DID work.”
Nice try but you will have to get up earlier than that to fool me.
This has obviously been infuriating you for the past 4 months. But you have learnt a lot.
[/SIZE][/FONT]
[/FONT][/COLOR]

Nope! It's exactly the circuit I posted. Look at the date it was designed!

Not a nice try but simply the truth.

#### colin55

##### Well-Known Member
Nope! It's exactly the circuit I posted. Look at the date it was designed!
Go back to the actual original circuit you posted. It contains none of the biasing components you have on the recent circuit, you have submitted.
I would have never criticised the latest circuit as it clearly allows the transistors to be turned off.
I don't think any of my students would be so bold as you. You must think I was born yesterday.

#### Boncuk

##### New Member
Go back to the actual original circuit you posted. It contains none of the biasing components you have on the recent circuit, you have submitted.
I would have never criticised the latest circuit as it clearly allows the transistors to be turned off.
I don't think any of my students would be so bold as you. You must think I was born yesterday.

That design just contains two resistors from base to ground (which aren't really necessary).

Of course you weren't born yesterday. May be that's the reason why you obviously overlooked the fact that I didn't post the circuit. It was posted by marvel6869.

If your students are not bold they must be "softies". I was paid for being bold for 23 years of my life.

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#### colin55

##### Well-Known Member
Here is the circuit you originally provided. The transistors will never turn off via the 555.

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#### colin55

##### Well-Known Member
Now you have added an extra diode and resistor to get the circuit to work. Exactly as I said in the first place. You had never tried and tested the original circuit.

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