I try to design analog buffer for the 5MSPS STM32 ADC. I try to use TSH114IDT or CLC4007 opamps ( I need 8 in total). I have done so far:

  1. Tried the design below with or without some of the elements - removing load , output capacitor, input capacitors etc.
  2. Single or dual supply.
  3. Unity gain or gain > 1
  4. Different configuations of the decoupling capacitors

My question: is it possible to design the stable buffer using those two OP-AMPS?


simulate this circuit – Schematic created using CircuitLab

The best I got: enter image description here

And the original waveform enter image description here

another not very successful attempts

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Example 1 on YouTube

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Example 2 on YouTube

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Example 3 on YouTube

  • 2
    \$\begingroup\$ Input a fixed DC voltage. Use the scope to grab a bunch of samples, then use the internal FFT to determine if the circuit is oscillating. Also show us the PCB layout. Is R1 really 100 ohm, or 100Kohm? Remove all the capacitors, and determine if the circuit is stable (you may need 10pF across R1, for stability in any circuit.) \$\endgroup\$ – analogsystemsrf Nov 25 '17 at 3:45
  • 1
    \$\begingroup\$ @analogsystemsrf I have tried. From the simplest ciruit to this one and its completely unstable. \$\endgroup\$ – P__J__ Nov 25 '17 at 9:14

Eventually I gave up and decided to use two OPAmps from CLC4007 in the inverting mode for one channel. In the inverting mode everything works perfect.


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