Please help review the schematic of RC4580.

Appreciate who can provide RC4580 TINA project ! thanks.

Gerry,

It is a bit odd to DC bias the second amplifier using the first amp's virtual ground DC value. Nevertheless it should work.

To get the circuit to work you need to remove C1620.

RC4580 output range should be a bout 1V to 4V with 5V VCC.

Hi Ron,

thanks for reply on this case, but actually we check the output 2, the signal is pretty noise. And I use OPA2677 to simulate it, and also see the output does not match my expectation. would you please help simulate it and send out the result. thanks a lot.

Gerry,

Can you share the Tina file to save me some time?

Hi Ron,

I used OPA2677 model.

OPA2677 - autosave 16-02-24 23_21.TSC

Hi Ron,

I complete the simulation with OPA2677 model, but not sure if this is workable for RC4580. please help check on it. thanks

OPA2677 - Oldboard.TSC

Gerry,

That was a horrible model. I couldn't even get it to make sense for DC analysis.

I made some edits and used LMV342 model instead. It is not a match, but it is much closer.

RC4580 has less output and input voltage range.

OPA2677 - (TLV342).TSC

Gerry,

Another way to do this it to make a single amplifier for the input signal (any gain needed) then use another amplifier to invert (gain = -1) the output of the first amplifier.

Hi Ronald

thanks a lot. last week we solve this issue on huawei's board. But one thing need to verify is the EMI problem, this issue was found last month while huawei was doing production certificate. because of that, huawei actually optimized their power supply, as you could see in the first post, there are ferrite beed and capacitor on the power supply to filter the noise on the power. But we are not sure if this could totally remove the EMI problem. we will test this after the new board coming back during March.