Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic 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

When an Operational Amplifier becomes an Operational Transconductance Amplifier?

Status
Not open for further replies.

swagata

Member level 3
Joined
Jul 4, 2007
Messages
63
Helped
4
Reputation
8
Reaction score
0
Trophy points
1,286
Activity points
1,684
When an Operational Amplifier becomes an Operational Transconductance Amplifier?
Provide me with relevant lecture notes if possible.
Thankyou
 

caosl

Advanced Member level 4
Joined
Mar 26, 2006
Messages
115
Helped
17
Reputation
34
Reaction score
4
Trophy points
1,298
Activity points
1,969
Re: OPAMP To OTA

When the load is a low value resistor or other alike, the OTA unable to drive it because of its' high output impendence. At this situation, you must add an output stage whch features a low impedence based on the OTA and provide enough current to load , generally, this an OP-amp.
 

    swagata

    points: 2
    Helpful Answer Positive Rating

A.Anand Srinivasan

Advanced Member level 5
Joined
Oct 15, 2005
Messages
1,804
Helped
257
Reputation
514
Reaction score
39
Trophy points
1,328
Location
India
Activity points
10,680
Re: OPAMP To OTA

ota is equivalent to opamp but its output is current... ota can be converted to opamp by using a common source amplifier at its output which converts the output to voltage... there is not much a difference other than this....
 

    swagata

    points: 2
    Helpful Answer Positive Rating

amriths04

Full Member level 5
Joined
Jul 15, 2006
Messages
266
Helped
23
Reputation
46
Reaction score
9
Trophy points
1,298
Activity points
2,831
Re: OPAMP To OTA

the output impedance impedance of an opamp is 0, but, that of an ota is a finite quantity. so the opamps that we actually design are ota's. when it is followed by a source follower it's output impedance is reduced thereby approximating an opamp.
 

    swagata

    points: 2
    Helpful Answer Positive Rating

ieropsaltic

Full Member level 4
Joined
Sep 25, 2006
Messages
199
Helped
64
Reputation
128
Reaction score
18
Trophy points
1,298
Activity points
2,595
Re: OPAMP To OTA

OTA relies mainly in its gain on high output resistance. Gain of any amplifier can be represented by Gm*Ro where Gm is the amplifier's transconductance and Ro is the output resistance. On using high values for Ro, higher gain can be achieved. The major drawback is that the OTAs can't drive loads of resistive nature because that would reduce Ro thus reducing gain. At this case (resistive loads), output buffers are required to keep the required gain (this buffer should have high input impedance) and the OTA becomes OPAMP. Unbuffered OTAs are used extensively when loads are of capacitive nature as in switched-capacitor circuits.
 

    swagata

    points: 2
    Helpful Answer Positive Rating

batistuta

Full Member level 1
Joined
Jun 14, 2007
Messages
95
Helped
4
Reputation
8
Reaction score
1
Trophy points
1,288
Activity points
1,845
Re: OPAMP To OTA

the ota has no buffer stage,but opamp has...
 

rajanarender_suram

Full Member level 4
Joined
Jan 20, 2006
Messages
215
Helped
22
Reputation
44
Reaction score
9
Trophy points
1,298
Activity points
2,375
OPAMP To OTA

Otas support only low Cap loads where as Opamps support caps as well resistive loads.
 

betty1007

Member level 1
Joined
Jan 15, 2007
Messages
39
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
1,478
OPAMP To OTA

OTA can only drive cap or large resistor,but op amp can drive low resistive loads
 

DZC

Full Member level 3
Joined
Sep 12, 2006
Messages
150
Helped
13
Reputation
26
Reaction score
4
Trophy points
1,298
Activity points
2,122
Re: OPAMP To OTA

betty1007 said:
ota+buffer=opamp
OPA-Buffer=OTA o(∩_∩)o...
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top