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amplification of operational transconductance amplifier

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simplsoft

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Hello

I want to ask about the amplification of operational transconductance amplifier (OTA). we always study OTA in form of transconductance. we dont see its gain then why is it called an amplifier. and why its used in instrumentation amplifiers etc. why OTA is prefered?

Thanx
 

There are various application of operational transconductance amplifier (OTA), Some are listed below.
1. design of simple amplifiers with voltage-controllable gain
2. design of firs-order and second-order active filters with controllable gains and controllable critical frequencies
Basically OTA is a voltage controlled current source thus gain is controlled by input voltage unlike conventional op-amp.
 

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Basically OTA is a voltage controlled current source thus gain is controlled by input voltage unlike conventional op-amp.

Yes - it can be seen as a voltage-controlled current source, however:
* The transonductance gm=d(Iout)/d(Vin) can be controlled by the bias current Iabc (separate control pin)
* The voltage gain is determined by the load resistor which converts the output current into an output voltage.
 

Thanx for your reply.

It means Op-amp and OTA are one and the same circuit..The difference is in op-amp the load is Resistor and in OTA the load is Capacitor.The whole circuit remains the same.
 

The difference is in op-amp the load is Resistor and in OTA the load is Capacitor.The whole circuit remains the same.
No. The circuits are different in so far that OP has an additional output stage. OTA has high output impedance (ideally infinite), OP has low output impedance (ideally zero).

OTA circuits use capacitive or resistive loads, depending on the application.
 

thanx for your reply.

The folded cascode OTA structure in sedra & smith books are mentioned as folded cascode OP-amps and in research article the same structure is mentioned as folded cascode OTAs.
 

In specific applications such as Gm-C filter or driving high capacitive load OTAs are used. Bias current Iabc in OTA can be tuned to adjust its gain.
 

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