Difference between OTA and OPAMP

[amitjagtap]

hi all,
can anybody tell me the basic 4 to 5 differences between OTA and OPAMP.
thanks in advance.

 

[carbon9]

Hi,

1. OPAMP works in voltage-mode i.e. its inputs and output(s) are all voltages, but OTA has voltage input and current output. Such devices are named as transconductance amplifiers.

2. OPAMPs ideally have infinite gains while OTAs have finite gain.

3. Most OPAMPs' gains are not adjustable in electronic means but OTAs' gains are adjusted by a control voltage/current.

4. Both OPAMP and OTA has infinite input resistance. But, output resistance is zero in an OPAMP and infinite in an OTA (of course ideally).

These are the main differences. But in application, since OTAs have current outputs, their application circuits are wider I think.

Regards,
carbon9

 

[amitjagtap]

This is ok,
I want to know more about their structural differences.

 

[sparso]

OTAs are basically Opamps without the output stage.
So you have the diff-amp and the gain stage. So
essentially most custom IC designs use OTAs as
you are most of the time driving known capacitive loads
so you can get away without the output stage.

Hope that helps.