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OpAmp OPA835 single rail design

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raff5184:

--- Quote from: Zero999 on September 19, 2019, 08:27:44 pm ---When you said in series, did you mean like this?
(Attachment Link)

--- End quote ---
Yes this is the type of series. Of course the 2 Vcc's are the same. Vref is derived from Vcc throuugh a 2426 type of virtual ground chip.
However I tried the circuit with these values but it gives a saturated 3MHz output

SiliconWizard:

--- Quote from: raff5184 on September 20, 2019, 01:56:05 pm ---
--- Quote from: Zero999 on September 19, 2019, 08:27:44 pm ---When you said in series, did you mean like this?
(Attachment Link)

--- End quote ---
Yes this is the type of series. Of course the 2 Vcc's are the same. Vref is derived from Vcc throuugh a 2426 type of virtual ground chip.
However I tried the circuit with these values but it gives a saturated 3MHz output

--- End quote ---

Do you mean that it's self-oscillating at 3MHz? If so, is the first stage oscillating, not saturating, and then the oscillation gets amplified by the second stage, which saturates?

Damianos:

--- Quote from: raff5184 on September 20, 2019, 01:56:05 pm ---
--- Quote from: Zero999 on September 19, 2019, 08:27:44 pm ---When you said in series, did you mean like this?
(Attachment Link)

--- End quote ---
Yes this is the type of series. Of course the 2 Vcc's are the same. Vref is derived from Vcc throuugh a 2426 type of virtual ground chip.
However I tried the circuit with these values but it gives a saturated 3MHz output

--- End quote ---
Since you are not showing the exact circuit, we can only guess!
For the moment, my guess is that, if you study a little more the datasheet, you will find what happens when using higher value resistors and what we can do to improve things (tip: put some capacitance in parallel with RF. Don't miss the reference to the loading of the amplifier (... these amplifiers are designed for a 2kΩ load...).

By the way, what is the input signal (shape) and how it is connected to the circuit?

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