Voltage to current amplifier

[sabahan]

I know that a voltage to current amplifier is called trans-conductance amplifier,but what does that means?convert voltage to current?than where the voltage comes from?or where the voltage goes to?
ohms law stated that current equals voltage divide by resistance,without voltage there are no current,as voltage increase current also increase,than what is all this about,voltage to voltage and voltage to current?

can anyone explain in a more non engineering term to me?I'm not a electronic engineer nor a electrical engineer.

 

[Harald Kapp]

It's well explained here.

 

[sabahan]

Thanks for the reply,but I still don't get it,is explain in the same manner that I have read online,it do produce current,it also product Vout,than why it is called a voltage to current amplifier and not a voltage to voltage or a current to current?

 

[Miguel Lopez]

The output of this kind of amplifier is a constant current, which depends only on the input voltage, not on the load (between certain limits). You can vary the load, and the current will be constant.

 

[sabahan]

Ok,that make sense,so it is actually a voltage control current source,am I right.

 

[Miguel Lopez]

That's right. Very useful in instrumentation, where a 4-20mA loop is used.

 

[KrisBlueNZ]

Any circuit that accepts a voltage signal and outputs a proportional current signal can be called a transconductance amplifier.

A voltage amplifier is defined, in basic terms, by the formula Vout = Vin * G, where G is the voltage gain of the amplifier.

A transconductance amplifier is defined by the formula Iout = Vin * gm, where gm is the mutual transconductance (transconductance relating output to input) of the amplifier.

Transconductance is measured in siemens or mhos (different names for the same thing). This unit is the reciprocal of resistance because it is I/V (resistance is V/I).

As well as the Wikipedia article on operational transconductance amplifiers, look up transconductance for a general explanation of what it means.