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

op-amp circuit schematic

Status
Not open for further replies.

perado

Full Member level 2
Joined
May 28, 2010
Messages
127
Helped
2
Reputation
4
Reaction score
2
Trophy points
1,298
Activity points
2,134
Hi
the attached schematic is an op-amp, which input pin is + and which one is - ?
 

keith1200rs

Super Moderator
Staff member
Joined
Oct 9, 2009
Messages
10,877
Helped
2,064
Reputation
4,128
Reaction score
1,597
Trophy points
1,403
Location
Yorkshire, UK
Activity points
57,276
Follow the signals through the circuit. If V2 goes lower, what happens to the output? It also goes lower. Therefore it is non-inverting.

Keith.
 
  • Like
Reactions: perado

    perado

    points: 2
    Helpful Answer Positive Rating

leo_o2

Advanced Member level 4
Joined
Sep 3, 2004
Messages
1,324
Helped
277
Reputation
556
Reaction score
240
Trophy points
1,343
Location
China
Activity points
5,761
When V2 is higher than V1, it leads to more current flowing thru the left branch and more current flowing thru M4. It will pull high Vo
 
  • Like
Reactions: perado

    perado

    points: 2
    Helpful Answer Positive Rating

perado

Full Member level 2
Joined
May 28, 2010
Messages
127
Helped
2
Reputation
4
Reaction score
2
Trophy points
1,298
Activity points
2,134
thanks for your replies

now I want to design an op-amp with the structure that I attached but I dont know I should start from where, can anybody help me? wich parameters are important in op-amp desin? Is this structure a good one?
 

leo_o2

Advanced Member level 4
Joined
Sep 3, 2004
Messages
1,324
Helped
277
Reputation
556
Reaction score
240
Trophy points
1,343
Location
China
Activity points
5,761
In fact, it depends on your application.
Generally, opamp spec are: input range, output range, min supply voltage, current consumption, slew rate, noise, offset, gain, phase margin, bandwidth, PSRR, CMRR.
 
  • Like
Reactions: perado

    perado

    points: 2
    Helpful Answer Positive Rating

perado

Full Member level 2
Joined
May 28, 2010
Messages
127
Helped
2
Reputation
4
Reaction score
2
Trophy points
1,298
Activity points
2,134
I want to use op-amp in this circuit :

 

dgnani

Advanced Member level 1
Joined
Jul 25, 2009
Messages
425
Helped
160
Reputation
322
Reaction score
152
Trophy points
1,323
Location
USA
Activity points
4,007
The opAmp you are planning to use will have to sink current from the RL resistor, what you trying to use is really an OTA, which usually handles only capacitive loads or very small currents. Unless RL is very large, you should probably add a buffer stage.
 

leo_o2

Advanced Member level 4
Joined
Sep 3, 2004
Messages
1,324
Helped
277
Reputation
556
Reaction score
240
Trophy points
1,343
Location
China
Activity points
5,761
I think you should consider these specs at the least:
stability(loop gain, phase margin, bandwidth), driving capability, input voltage range, slew rate, offset influence.
 

perado

Full Member level 2
Joined
May 28, 2010
Messages
127
Helped
2
Reputation
4
Reaction score
2
Trophy points
1,298
Activity points
2,134
hi
which structure is good for use at this circuit?
The opAmp you are planning to use will have to sink current from the RL resistor, what you trying to use is really an OTA, which usually handles only capacitive loads or very small currents. Unless RL is very large, you should probably add a buffer stage.
 

dgnani

Advanced Member level 1
Joined
Jul 25, 2009
Messages
425
Helped
160
Reputation
322
Reaction score
152
Trophy points
1,323
Location
USA
Activity points
4,007
a two stage Miller opamp seems a better fit but it really depends on the signal coming from Zin and its impedance (looking in the opposite direction to the arrow in your schematic), basically what determines the load of the op amp
As simple way to verify you have the right specs for your op amp (DC gain, bandwidth, output resistance, slew rate,...) is to implement it first as an ideal op amp with the specs you are planning to target in the actual design; until the ideal design works there is no reason to start designing the real thing
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top