Unbuffered OPAMP and OTA

[sudhanwaaa]

Hello,
You guys may find my question silly.But I want to ask the term "unbuffered OPAMP" used by author of "CMOS Analog circuit design" and the concept of "OTA(OPERATIONAL TRANSCONDUCTANCE AMPLIFIER ) "same?What exactly is "Iabc " terminal of OTA?

 

[bigdogguru]

TI offers a good appnote on OTAs:

Demystifying the Operational Transconductance Amplifier (OTA)

And the following tutorial discusses I_ABC:

Active Filter Design Using Operational. Transconductance Amplifiers: A Tutorial.


BigDog

 

[LvW]

What exactly is "Iabc " terminal of OTA?

The OTA is an operational amplifier with a high-resistive "current" output - in contrast to the classical voltage-opamp (low-resistive voltage output).
OTAs are characterized by their output-to-input relation which is current-to-voltage ratio (transconductance gm).
More than that, this transconductance is dermined by a DC current which is externally applied (determining the internal DC quiescent current).
This current is called "Amplifier Bias Current" (Iabc).

 

[sudhanwaaa]

Thnx for the links.I have already read these articles.My question is what is
unbuffered OPAMP ? Does it have any relation with OTA ?

 

[hafeez.kt]

OTA + Buffer = Op Amp

unbuffered OPAMP is the OTA