# Voltage amplification using opAmp, getting square wave for a sinusoidal signal , How to overcome?

#### ashokraj

Joined Feb 1, 2018
128
I am looking for an operational amplifier( through hole) which can give me a 3V peak to peak when the input is 220mV Peak to peak. Firstly, Will it be possible ? I am currently using LM324N and tested the circuit with the following circuit diagram and simulation results ( Found this circuit from other threads).

I have opted for different resistor values.
R5 and R4 100k.
R3 and R10 9.1K
R1 330K
R2 1K
C1 and C2 22u

It is driven by single supply with 5V

My output is as follows:

will it be possible to get the sinusoidal signal as the ouput with 3V peak to peak with the input of 220mV? I am looking for some amplifier which exactly replicates my input signal. The problem with my attached link is if the voltage is very less i.e., 200mV or 500mV irrespective of the input( ramp, sinusoidal) output is a square wave.

while selecting an opamp for this specific purpose what are the parameters i need to keep into consideration?

Any circuit diagram would be beneficial to me.

-
Thanks,
Ashok

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#### AlbertHall

Joined Jun 4, 2014
12,231
What values did you use for the two resistors?
What voltages were the positive and negative supply for the amplifier?

#### Ylli

Joined Nov 13, 2015
1,063
From TS "non inverting amplifier using single supply."

#### AlbertHall

Joined Jun 4, 2014
12,231
From TS "non inverting amplifier using single supply."
From the attached oscilloscope image of the output, the signal goes both positive and negative. Now it may be that the output signal is AC coupled or there may be a dual supply.

If it is a single supply, then the negative supply would 0V.

In any case the gain is higher than intended so it would seem there is a problem with the gain setting resistors.

#### bertus

Joined Apr 5, 2008
22,141
Hello,

I assume you are using the following circuit:

What are the resistor and capacitor values you are using?
What is the supply voltage?

Bertus

#### ashokraj

Joined Feb 1, 2018
128
What values did you use for the two resistors?
What voltages were the positive and negative supply for the amplifier?
R5 and R4 100k.
R3 and R10 9.1K
R1 330K
R2 1K
C1 and C2 22u

It is driven by single supply with 5V.

#### ashokraj

Joined Feb 1, 2018
128
Hello,

I assume you are using the following circuit:

View attachment 160484

What are the resistor and capacitor values you are using?
What is the supply voltage?

Bertus
Bertus,
As below:
R5 and R4 100k.
R3 and R10 9.1K
R1 330K
R2 1K
C1 and C2 22u
Supply is around 5V.

#### bertus

Joined Apr 5, 2008
22,141
Hello,

I don't see R5 and R10 in the schematic.

Bertus

#### ashokraj

Joined Feb 1, 2018
128
Hello,

I don't see R5 and R10 in the schematic.

Bertus
apologies Bertus,
Here is the circuit and simulation results.

#### ericgibbs

Joined Jan 29, 2010
17,419
hi,
Is this option suitable for your application.?
E

#### ashokraj

Joined Feb 1, 2018
128
hi,
Is this option suitable for your application.?
E
View attachment 160491
Eric,
may i know what is the simulation software you are using? yes that is suitable for my application. I will try with POTS and will get back.
Also, what is the meaning of sine(0 110 1000)? I am new to this!

#### ericgibbs

Joined Jan 29, 2010
17,419
hi,
If you are using the same feedback resistor value for the OPA, which is designed for +/-10mV input and you apply a +/-110mV you will get a square wave output.
The OPA is limiting.
Look at post #12, note the reduced value of R1, set now for a +/-110mV input.
E

#### ericgibbs

Joined Jan 29, 2010
17,419
hi,
Also, what is the meaning of sine(0 110 1000)? I am new to this!

Sine means a sine wave signal
0 means 0V offset at the Input
110m means +/-100mV sine wave signal ie: 220mVppk
1000 is the frequency of the Sine wave.
E

#### ashokraj

Joined Feb 1, 2018
128
hi,
Also, what is the meaning of sine(0 110 1000)? I am new to this!

Sine means a sine wave signal
0 means 0V offset at the Input
110m means +/-100mV sine wave signal ie: 220mVppk
1000 is the frequency of the Sine wave.
E
Thanks for the valuable info

#### ashokraj

Joined Feb 1, 2018
128
hi,
Also, what is the meaning of sine(0 110 1000)? I am new to this!

Sine means a sine wave signal
0 means 0V offset at the Input
110m means +/-100mV sine wave signal ie: 220mVppk
1000 is the frequency of the Sine wave.
E
Hello Eric,
Thanks for the circuit. May i know how did you determine the values of resistor and capacitor. is there any application notes/pdf available online/google. The circuit published by you is working the way i want.

#### ericgibbs

Joined Jan 29, 2010
17,419
hi ashok,
This PDF covers the basics of OPA's.
E

EDIT:
Ref page #76

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