Quote:
For example if you say this is voltage amplifier, is it mean that it doesn't need current and when you say it is current amplifier is it mean it doesn't need voltage.
Nobody has claimed, that voltage or current are "not needed". For example, a voltage amplifier simply has the
task to amplify voltages (as good as this can be achieved in hardware!). And, of course, there will be currents flowing.
Another good example is the BJT: Some people - and even some good and serious textbooks - state that the BJT is a current driven device because of Ic=hfe*Ib.
However, from the "cause and effect" point of view, cetainly this is wrong. A small current Ib never can be the cause for a larger current Ic. Instead, the BJT is voltage controlled (or even more exact: charge controlled) - even if an "input current" is applied (which, in fact, is nothing else than a voltage applied through a very large source resistance).
More than that, since several years the so called "current mode approach" in analog signal processing is discussed in a lot of papers and conference contributions. Here, all IC-internal signals are represented as currents - however, the cause of these currents always are voltages.
---------- Post added at 08:41 ---------- Previous post was at 08:09 ----------
As far as the question "current or voltage mode" is concerned, there are some very instructive contributions from a swiss author
Hanspeter Schmid which can be found and identified via google.
As an example, here is one reference (magazine):
Analog Integrated Circuits and Signal processing (35), 2003,pp. 79-90. Kluwer Academic Publishers.
---------- Post added at 09:52 ---------- Previous post was at 08:41 ----------
You understand, so why get caught up in the semantics. Humans are air, water and food dependent devices, but to say we need air doesn't exclude the other requirements. We say that some things are voltage or current dependent to indicate which parameter must be controlled to achieve a desired performance. It's understood that Ohm's law is not invalidated by our desire to simplify our terminology.
KJ6EAD, I cannot agree with you. I assume you are an experienced engineer.
But can you really not understand when somebody (who most probably is a beginner in electronics) is getting "caught up in the semantics" ?
Of course, it is a common desire to "simplify our terminology".
But don`t forget that such a simplification is the
second step!
As a
first and most important step you have to
understand what's going on in resistors, transistors and what is the
physical cause of some effects!
And, of course, this touches the relations between voltages and currents.
For example: Is the solar cell a voltage or a current source - and is the answer to this question of any importance?
Or another question (mentioned already in my former answer): Is the BJT current or voltage controlled?
Simplification is good and necessary - otherwise the gain formula for an opamp with feedback would consist of more than 50 terms! However, at first you have to proove which pameter in which particular application can be neglected. But this can be done only if you have a sufficient understanding.
As you know - in electronics nothing is 100% correct; even not the simple voltage-current relationship (Ohms law) in a resistor. But when you know the cause and the amount of disturbances you can assess the influence of these effects which are called "parasitic". But at first, you have to understand!
Having this in mind I completely understand and appreciate the questions from TAHIR4AWAN.
Regards
LvW