buffers and voltage regulators

[yyyyaser]

when is it recommended , and when do i have to use:

- voltage regulators .

- buffers .

thanks in advance .

 

[crutschow]

Depends upon whether you want to buffer a signal or regulate its voltage.

 

[dknguyen]

A regulator takes a wide range of voltage in and turns it into a a single output voltage with a usable amount of current.

A buffer takes a signal in and outputs the same signal without nearly as much current.

They're two different things with no overlap so your question doesn't make much sense. So yeah, basically you use a regulator regulate and a buffer to buffer.

 

[yyyyaser]

what i mean is , for example:

- Do i have to use the voltage regulator when the energy source is a battery or an adaptor from ac source .

- Do i have to use a buffer between each two components .

 

[dknguyen]

1. You only need one if your components require a stable, clean, specific voltage and your power source (whether it's AC, DC, from a battery, or whatever) does not meet these requirements. You can have the best 12V voltage source in the universe, but if your components need 5V (that can reduce 12V to 5V), you still can't connect the two directly. If your components need clean, stable 5V and you have a crappy 5V voltage source that keeps jumping between 4V and 6V, then you'll need a regulator (one that can increase AND decrease voltage so it can turn any voltage between 4V and 6V into 5V).

Remember, that not all regulators do the same thing- many only decrease voltage, some only increase voltage, and some can increase or decrease voltage. So you might need specific types of regulators for certain combinations of voltage sources and circuit components.

ANd please remember the conservation of energy. Power in = power out. So you can take extra current and turn it into extra voltage, or take extra voltage and turn it into extra current. So regulators can do:
Low Voltage, High current -> High voltage, low current
High Voltage, Low current -> Low voltage, high current
What they can't do is magically increase both voltage and current since the extra power has to come from somewhere.

2. It depends on the components you are trying to connect. You definately don't do it everywhere since it would make your circuit very large and expensive. Usually you use a buffer between output-input connection when the output impedance cannot be considered "much smaller" than the input impedance (said another way, the input impedance cannot be considered "much larger" than the output impedance). How "much" depends on how much distortion you can tolerate in the transmission of the signal which depends on the circuit and what you are trying to do.

Low input impedances are hard to drive and high output impedaces are bad at driving so you want the input impedance to be much higher than the output impedance and this will result in distortion of the signal. Ideally you want the input impedance to be zero and the output impedance to be infinite, so you want to approximate this scenario as close as possible when connecting components. Sometimes you can't. So what do you do when you have driver with a high output impedance and receiver with low input impedance? You stick a buffer between them! The buffer reproduces the input signal it sees at it's output which makes it seem just like a piece of wire...but it's not. The buffer is chosen so that it's input impedance is MUCH higher than the output impedance of the driver and is also chosen so that it's output impedance is MUCH lower than that of the receiver.

So at first you have:
High Output Impedance -> Low Input Impedance (BAD!)

But a properly chosen buffer look like:
->Even Higher Input Impedance + Even Lower Input Impedance ->

And when you add the buffer into the connection you get:
High Output Impedance ->Much Higher Input Impedance + Much Lower Input Impedance -> Low Input Impedance

Now you have no problems because every output impedance is now "much smaller" relative to the input impedance it is driving and every input impedance is being driven by an output impedance that is "much larger".

 

[yyyyaser]

cant thank you enough .