frankzappa
Well-known member
Hello!
I just saw this document: https://www.eetimes.com/using-op-amps-with-data-converters-part-1/#
Part 2: https://www.eetimes.com/using-op-amps-with-data-converters-part-2/
Part 3: https://www.eetimes.com/using-op-amps-with-data-converters-part-3/
There are multiple parts in this series and it basically says that buffering op amps must be matched to the ADC or they may not perform properly.
Most often you have to test which op amps work best with a given ADC in your specific application. Also the ADC manufacturer often has recommended op amps.
Are there such op amp recommendations from the manufacturer of the teensy4 adc?
I have tested the Texas Instruments TLC2264 which seems to work fine on my PCB and the Microchip MCP6004 only on a breadboard. I have a PCB coming in with the MCP6004 so will be able to compare them. Breadboards are much noisier.
Maybe people on this forum has tested some op amps and can give recommendations?
I just saw this document: https://www.eetimes.com/using-op-amps-with-data-converters-part-1/#
Part 2: https://www.eetimes.com/using-op-amps-with-data-converters-part-2/
Part 3: https://www.eetimes.com/using-op-amps-with-data-converters-part-3/
There are multiple parts in this series and it basically says that buffering op amps must be matched to the ADC or they may not perform properly.
Most often you have to test which op amps work best with a given ADC in your specific application. Also the ADC manufacturer often has recommended op amps.
Are there such op amp recommendations from the manufacturer of the teensy4 adc?
I have tested the Texas Instruments TLC2264 which seems to work fine on my PCB and the Microchip MCP6004 only on a breadboard. I have a PCB coming in with the MCP6004 so will be able to compare them. Breadboards are much noisier.
Maybe people on this forum has tested some op amps and can give recommendations?
The most obvious requirement for a data converter buffer amplifier is that it not degrade the dc or ac performance of the converter. One might assume that a careful reading of the op amp datasheets would assist in the selection process: simply lay the data converter and the op amp datasheets side by side, and compare each critical performance specification. It is true that this method will provide some degree of success; however, in order to perform an accurate comparison, the op amp must be specified under the exact operating conditions required by the data converter application. Such factors as gain, gain setting resistor values, source impedance, output load, input and output signal amplitude, input and output common-mode (CM) level, power supply voltage, and so forth, all affect op amp performance.
It is highly unlikely that even a well written op amp data sheet will provide an exact match to the operating conditions required in the data converter application. Extrapolation of specified performance to fit the exact operating conditions can give erroneous results. Also, the op amp may be subjected to transient currents from the data converter, and the corresponding effects on op amp performance are rarely found on datasheets.
Converter datasheets themselves can be a good source for recommended op amps and other application circuits. However this information can become obsolete as newer op amps are introduced after the converter's initial release.
Analog Devices and other op amp manufacturers today have on-line websites featuring parametric search engines, which facilitate part selection (see Reference 1). For instance, the first search might be for minimum power supply voltage, e.g., 3 V. The next search might be for bandwidth, and further searches on relevant specifications will narrow the selection of op amps even further. Figure 3-4 summarizes the selection process.
The amplifier should not degrade the performance of the ADC/DAC
Ac specifications are usually the most important
– Noise
– Bandwidth
– Distortion
Selection based on op amp data sheet specifications difficult due to varying conditions in actual application circuit with ADC/DAC:
– Power supply voltage
– Signal range (differential and common-mode)
– Loading (static and dynamic)
– Gain
Parametric search engines may be useful
ADC/DAC data sheets often recommend op amps (but may not include newly released products)