Continue to Site

# Problem with ampilifying with an op-amp

Status
Not open for further replies.

#### baby_1

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?

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.

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?

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?

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:

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

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.