# Op amp gain decreases after some point as I try to increase it.

Discussion in 'The Projects Forum' started by kontakis, May 1, 2015.

1. ### kontakis Thread Starter New Member

Feb 21, 2012
1
0
I used OPA 544 to construct this non-inverting amp circuit. Except I used 2.7Kohm as R2 and replaced R1 with a 1K potentiometer. My supply is +24V -24V. The gain should increase as I decrease the value of potentiometer but after gain exceeds 5, output starts to get trimmed from the bottom and gain starts to decrease until output disappears. Really new to electronics and sorry if this is a simple issue. Btw I'm using a sinus wave well within the bandwith and RL is 160 ohm. I'm inputting the signal from the audio jack of my pc. Also the clipping occurs at gain of 5 regardless of input amplitude. If I input Vp-p= 1V it gets clipped at Vout p-p=5V and If I input Vp-p= 2V it gets clipped at Vout p-p=10V and so on.

2. ### pwdixon Member

Oct 11, 2012
488
56
Sounds like a dc offset problem.

3. ### MikeML AAC Fanatic!

Oct 2, 2009
5,451
1,066
What is the load? You are likely exceeding the maximum current allowed for the opamp.

4. ### ScottWang Moderator

Aug 23, 2012
4,934
777
Do you want to try some uppfer values of resistors
This is a power op map and the max current about 4A.

5. ### ScottWang Moderator

Aug 23, 2012
4,934
777
Do you want to using higher resistors as R2 = 10K, R1 was using 2.4K in series with 1K pot.

6. ### MikeML AAC Fanatic!

Oct 2, 2009
5,451
1,066
Then have you checked the supply voltages to see if you are exceeding their maximum current?

Is the amp mounted on a suitable (quite large) heatsink?

7. ### ScottWang Moderator

Aug 23, 2012
4,934
777
As the TS using RL=160 Ω and the Vout = 10 Vmax, I = 10V/160Ω = 62.6mA.

8. ### MikeML AAC Fanatic!

Oct 2, 2009
5,451
1,066
Still leaves the question about the supplies, and the heatsink?

9. ### ScottWang Moderator

Aug 23, 2012
4,934
777
And what do you calculate their values?