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

Thread Starter

ashokraj

Joined Feb 1, 2018
87
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:


https://drive.google.com/open?id=1bpUAuofjfqc9WjjbQrOEimKDiBwhkl_W



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
 
Last edited:

AlbertHall

Joined Jun 4, 2014
9,875
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
20,540
Hello,

I assume you are using the following circuit:

radio-electronics-op-amp-non-inverting-circuit-single-rail.gif

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

Bertus
 

Thread Starter

ashokraj

Joined Feb 1, 2018
87

ericgibbs

Joined Jan 29, 2010
10,054
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
10,054
hi,
I am using LTSpice, its a free download.
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
 

Thread Starter

ashokraj

Joined Feb 1, 2018
87
hi,
I am using LTSpice, its a free download.
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
 

Thread Starter

ashokraj

Joined Feb 1, 2018
87
hi,
I am using LTSpice, its a free download.
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.
 
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