LMH6626: LMH6626 Output in non inverting mode

Gavi Siddu

Part Number: LMH6626
Other Parts Discussed in Thread: OPA2846

I am using LMH6626 in non-inverting mode with Rf=690R and Rg=84R for a gain value of 9.52. I am building the circuit by taking the reference from the datasheet, but the out is not stable throughout the frequency from 1khz to 20mhz. I am getting different values of output. I am supplying +/-6v for the Op Amp.

Can somebody help me with this?

over 5 years ago

0 Shreenidhi Patil over 5 years ago

TI__Expert 3126 points

Can you please share the circuit here ?

along with the output waveform captured on the scope .

0 kai klaas69 over 5 years ago

Guru 140200 points

Hi Gavi,

what do you mean by "not stable"? Can you specify please?

Kai

0 Gavi Siddu over 5 years ago in reply to kai klaas69

Prodigy 240 points

According to the design it needs to produce 9 Vpp but its producing lower values

0 kai klaas69 over 5 years ago in reply to Gavi Siddu

Guru 140200 points

Hi Gavi,

but please give some numbers.

Kai

0 Gavi Siddu over 5 years ago in reply to kai klaas69

Prodigy 240 points

I am supplying +/-5v and getting output of 8.8vpp at 1Khz at this frequency the peak of the output is getting clipped , i am feeding 2vpp signal to opamp with 1vdc offset.

0 kai klaas69 over 5 years ago in reply to Gavi Siddu

Guru 140200 points

Hi Gavi,

your input signal is much too large! 2Vpp x 9.52 = 19.04Vpp!

Also, the output of LMH6626 cannot fully reach the supply rails but stays about 1V away from them. So, an output voltage swing of 8.8Vpp is absolutely normal with a +/-5V supply.

Kai

0 Gavi Siddu over 5 years ago in reply to kai klaas69

Prodigy 240 points

I need to achieve an output of 10vpp (9vpp to 10vpp is also okay) throughout the frequency range of 1khz to 20Mhz. But as i previously mentioned there is some clipping in the output waveform at lower frequency say 1KHZ.

0 Michael Steffes over 5 years ago in reply to Gavi Siddu

Guru 48165 points

You are using a dual decompensated device slightly lower the min stable gain, also, your 10Vpp at 20Mhz exceeds the slew rate in the LMH6626. Try using the OPA2846 on +/-6V supplies.

Also, you need to provide a circuit for more insight.

0 Michael Steffes over 5 years ago in reply to Michael Steffes

Guru 48165 points

And actually, the OPA2846 has too much headroom requirement as well for a 10Vpp swing. But, on +/-6.4V supplies you can get 9Vpp safely. Right on the edge slew rate wise. Again a schematic would help - sometimes other things in the full schematic can show where your current issue might be.

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LMH6626: LMH6626 Output in non inverting mode