OPA548: OPA548 Positive side clipping within the supply range

Hi,

your circuit is instable because of the way too high capacitive load:

saravan_opa548.TSC

Kai

hey Kai,

Thanks for your response. Yeah we have removed those output load capacitor. Still we are observing the same positive side clipping.

saravan

Hi saravan, 

saravanakumar Dinakaran said:

But i am getting the output positive clipped at 12.9VPP. Kindly suggest i am attaching my schematics for your reference.

OPA548 is not RRIO amplifier. As the load current increases, there will be less head room to swing up to ±15Vdc. With 15Vdc - 12.9Vdc = 2.1Vdc, this output swing losses are expected, see the datasheet capture and simulation below. If you want to increase the output voltage swing, you have to increase the level of supply rails. Also, your input voltage signal is too large, With Gain = 10 V/V, the input voltage swing should be less than 1.29Vpk or 2.58Vpp. 

OPA548 Clipping Issues 02282023.TSC

If you have additional questions, please let us know. 

Best,

Raymond

Hi Raymond,

Thanks,  You are right, I connected 0 OFFSET input 6.5Vpp. Any suggestion to bring my input offset 3.25V. So that my signal will become + or - 3.25Vpp input to OPA548.

Saravan

Hey Raymond 

 Thanks for your support,  issue solved.

I am asking an another question :

Output of OPA548 (26Vpp)  given as an input of OPA455. The final output of OPA455 is 120Vpp and output current of the OPA455 is 45mA  but i need to drive 500mA load. Now my question is how to boost output current of my circuit from 45mA to 500mA. kindly suggest.

Regards

Saravanakumar D 

Hi,

why hot taking a speaker amplifier like the LM3886, or similar?

Kai

Hi,

LM3886 VCC  limited to +/-35V. any other suggestion.

Thanks

saravan

saravanakumar Dinakaran said:

LM3886 VCC  limited to +/-35V.

No, it is not. +/-35V is the maximum recommended supply voltage in combination with a 8R load. But 500mA at 60Vpeak means a load of about 120R and for this load the supply voltage can be higher.

Nevertheless, the LM3886 will do in a bridge configuration even with a supply voltage of +/-35V:

sara_lm3886.TSC

Kai

Hi Kai,

1. I am planning to add this circuit and try in my design. Tanks for your help. I think the same circuit is enough right ?. 

2. We are finding difficult to source the component LM3886. If we replace the IC with  LM2876 by reducing our output requirement to 105Vpp will it work. 

Regards

Saravanakumar D