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

Problem with ampilifying with an op-amp

Status
Not open for further replies.

baby_1

Advanced Member level 1
Joined
Dec 3, 2010
Messages
415
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,298
Activity points
4,277
i use TL081 for my basic circuit
i use two resistor (R1(feedback)=10K and R2(input)=1K at - input pin)
i connected the + input pin to Ground.
i connect an ac signal to R1 with 10mili Volt(vp-p) value.
when i see the output from the output has some distorbution and it doesn't amplify it.

i baias it with 12 volt (pin 4 to ground and 7 pin to VCC)

what is my problem?
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
47,494
Helped
14,051
Reputation
28,357
Reaction score
12,709
Trophy points
1,393
Location
Bochum, Germany
Activity points
276,187
Re: ampilify with op-amp

The most simple solution is a bipolar supply, connect a negative voltage to pin 4. Otherwise you have to design a suitable circuit for single supply. You particularly have to observe the specified input voltage range of TL081. It doesn't inlude the negative supply.
 

baby_1

Advanced Member level 1
Joined
Dec 3, 2010
Messages
415
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,298
Activity points
4,277
Re: ampilify with op-amp

now what can i do for a normal power supply(dc-0-12Volt and o is my ground)?

---------- Post added at 16:31 ---------- Previous post was at 16:31 ----------

and could you tell me how can i create a negetive voltage?
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
47,494
Helped
14,051
Reputation
28,357
Reaction score
12,709
Trophy points
1,393
Location
Bochum, Germany
Activity points
276,187
Re: ampilify with op-amp

You don't need to generate a negative voltage, the amplifier can designed for single supply, even with a TL081. Some points haven't been specified yet:
- AC or DC amplification intended?
- acceptable or required output voltage bias?
 

Syncopator

Full Member level 6
Joined
Dec 15, 2010
Messages
368
Helped
70
Reputation
140
Reaction score
66
Trophy points
1,308
Location
N.E. Lincolnshire U.K.
Activity points
3,395
Re: ampilify with op-amp

now what can i do for a normal power supply(dc-0-12Volt and o is my ground)?[
Connect two 10k resistors in series across your 12V supply. Decouple their junction to one of the rails (pos or neg -doesn't matter which). Use their junction as the circuit common, 0V. You then have +6 and -6V. The input voltage/signal should be between 0V and R2. The output signal between the output pin and 0V. The non-inverting input of the amplifier connected to 0V


 
Last edited:

Miguel Gaspar

Advanced Member level 1
Joined
Mar 6, 2006
Messages
479
Helped
70
Reputation
140
Reaction score
34
Trophy points
1,308
Location
Culiacán, Sinaloa, Mexico
Activity points
4,971
Re: ampilify with op-amp

It doesn't work because the output voltage swing is less by about 1.2volts so your operating area is form 1.2V to 11.8V. But your signal gose from negative voltages to +0.1V, that is outside te swing range.
If you have only one Power supply, you can try this circuit, but tha output will have a DC offset. See the circuit

 

kak111

Advanced Member level 4
Joined
Mar 30, 2011
Messages
1,366
Helped
933
Reputation
1,868
Reaction score
907
Trophy points
1,413
Location
Finland
Activity points
10,942
Re: ampilify with op-amp

If you add capacitor for in- and output
and select values R3 and R4 are equal ( 1k )
You get an ac-amplifier behaving like it has +/-6V power supply

KAK
 
Last edited:

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top