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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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