Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Difference between Op Amp and Transconductance Amp

Status
Not open for further replies.
M

mengghee

Full Member level 3
Joined
Nov 29, 2005
Messages
163
Helped
8
Reputation
16
Reaction score
5
Trophy points
1,298
Location
United Kingdom
Activity points
3,105
Can anybody tell me the difference between the op amp and transconductance amplifier ?
 

Opamp is used to drive loads which are resistive or capacitive, whereas OTAs are used to drive purely capacitive loads(small cap loads). Also except for the input/output node all other nodes in an OTA are low impedance nodes unlike an opamp. Usually an OTA has 2 stages with no buffer, whereas an Opamp has a buffer stage. If you need more information regarding design, please refer to the Book CMOS circuit design by baker and Boyce.
 

    M

    mengghee

    Points: 2
    Helpful Answer Positive Rating
I am very new towards amp design.... what does purely resistive or capacitive load refer to ? can you give me a simple example of an implementation ? thank you very much
 

suhas_shiv said:
Opamp is used to drive loads which are resistive or capacitive, whereas OTAs are used to drive purely capacitive loads(small cap loads). Also except for the input/output node all other nodes in an OTA are low impedance nodes unlike an opamp. Usually an OTA has 2 stages with no buffer, whereas an Opamp has a buffer stage. If you need more information regarding design, please refer to the Book CMOS circuit design by baker and Boyce.
Click to expand...


in my opinion, the load for OTA is not purely capacitive load because of the effect of itself output resistive load
 

    M

    mengghee

    Points: 2
    Helpful Answer Positive Rating
When I say the load, I mean to say the stage after the OTA. If you consider a CMOS differential amplifier, its input is dominated by capacitance. Also, purely resistive and capacitive means that either the resistance or capacitance dominates( when I say purely, I don't mean to say literally, I guess the usage of the word purely was misleading, sorry for that). Refer the above book and maybe your doubts will be cleared.
 

I am getting more confuse. sorrie.... wondering if you can explain more... thank you
 

Please go thru the book CMOS circuit design, simulation and layout by Baker and Boyce. It will give you some basic understanding about opamps and OTAs. If you still have doubts, I will try to help you out.
 

    M

    mengghee

    Points: 2
    Helpful Answer Positive Rating
mengghee said:
I am very new towards amp design.... what does purely resistive or capacitive load refer to ? can you give me a simple example of an implementation ? thank you very much
Click to expand...

or more simple way to understand is :

1. resistive load- when there is a path current sink to ground like driving resistor.
2. capacitive load- current have has no path sink to ground and only charge up
the capacitive load like driving capacitor.
 

    M

    mengghee

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top