# TL072 opamp clipping problem

I'm trying to drive a TPA6120 headphone amplifier with TL072. I use single 24VDC supply with a TLE2426 virtual ground.

The TL072 works well and puts out around 21Vp-p sine wave. But as soon as I connect the TPA6120 amplifier to its output the sine gets clipped to around 17-18Vp-p. That is 6V less than supply voltage. Any idea wahat could cause this? Looking at TL072 datasheet Figure 6-12 and 6-13, output swing with 1k load (12mA@+-10V) should still be atleast 22V.

• The sine looks ok from first TL072 output.(Yellow line on scope screen)
• The sine comes out clipped from second stage(Blue line on scope screen)
• The signal then enters TPA6120 which is loaded with 16 ohm resistor at its output.

• Your amp is very strong. Decrease amplitude of your signal or select other power supply. Try change R23. Dec 14, 2020 at 19:53
• I will be driving a very high impedance headphones(400 ohm) so the power will not be as high actually. By select other power suply you mean higher voltage? Dec 14, 2020 at 20:00
• Issues I see with this circuit: 1) Why are there 2 opamps present? I think IC7D and R23 are not needed. To get more gain you can make R17 = 20 kohm. 2) I do not see how VGND12V is created. Dec 14, 2020 at 20:01
• @Bimpelrekkie 1) , 2) I updated the schematic, there was a mistake. Dec 14, 2020 at 20:14
• Why are R38 & R37 so low (1k)? IC7D has trouble driving a 1k load. Try increasing these two resistors to 3.9k. Dec 14, 2020 at 21:36

$$\V_{OM}\$$ is the maximum peak voltage output swing. They give values $$\V_{OM}\$$ for various $$\R_L\$$ values.
When $$\R_L\$$ is greater than 2K$$\\Omega\$$, but less than 10k$$\\Omega\$$, they only guarantee $$\V_{OM}\$$ to be 10V. Sad but true. That is a full 5V below the +15V rail.
Your supply is 24V, with a virtual ground, so we will call it +/- 12V. Slightly different scenario, but you can see that if the spec only guarantees 10V with a +15V supply, it wouldn't be surprising if loading your op amp with less than 10K$$\\Omega\$$ $$\R_L\$$ at +/- 12V supply would clip at 8.5-9.0V. :-(