This one from ADI will also do well. It is a bit fast, so you would need to be a bit careful.
https://www.analog.com/media/en/technical-documentation/data-sheets/ADA4898-1_4898-2.pdf
Best, Sandro
https://www.analog.com/media/en/technical-documentation/data-sheets/ADA4898-1_4898-2.pdf
Best, Sandro
In my country, it hard to get good op-amp. We must import, expensive.
Good op-amp can meet can those spec., expect harmonic profile is not monotonic. I think because very low bias current at output transistor.
It is fun if I can make it. It is about DIY after all.
Oh, if it is for the fun of DIY, yes, go for it!
If you want ICs for cheap, you can always order samples 🙂.
Just pay for the shipping.
If you want ICs for cheap, you can always order samples 🙂.
Just pay for the shipping.
See post #3 - full discrete. Has a capacitance multiplier in the power supply rails. Close to LM4562 values and far lower output impedance. Offset can be regulated.
Have fun, Toni
I have designed it using output class A single-ended. I share it at local audio community. Someone tested using SMD component. He sent me 4 pairs for free to me. But I don't test it, yet.
That's designed for low-impedance only, the current noise is very high. The datasheet calls a feedback resistor > 300 ohms "large", and that's about the optimim value, noise-wise. Not a general purpose audio opamp.
Hi Mark, the current noise is high (2.4pA/rtHz) because the voltage noise is low (0.9nv/rtHz). To achieve the latter, you need to bias the input transistors at a high current, which results in the former. The AD797 has exactly the same problem with a current noise of 2pA/rtHz.
Regarding the 300 ohms, it has to do with stability, not noise. Low voltage noise needs large input devices, which leads to large input capacitance. Since the amp is fast (65MHz), use a large RF and you get an oscillator. From the datasheet:
"HIGHER FEEDBACK RESISTOR GAIN OPERATION
The ADA4898-1/ADA4898-2 schematic for the noninverting
gain configuration shown in Figure 45 is nearly a textbook
example. The only exception is the feedback capacitor in
parallel with the feedback resistor, RF, but this capacitor is
recommended only when using a large RF value (>300 Ω).
Figure 46 shows the difference between using a 100 Ω resistor
and a 1 kΩ feedback resistor. Due to the high input capacitance in
the ADA4898-1/ADA4898-2 when using a higher feedback
resistor, more peaking appears in the closed-loop gain"
Is it general purpose... well no (curent noise is high and it is a tad too fast to be bullet proof). But, its no more general purpose than the AD797 which everyone loves.
Best, Sandro
Regarding the 300 ohms, it has to do with stability, not noise. Low voltage noise needs large input devices, which leads to large input capacitance. Since the amp is fast (65MHz), use a large RF and you get an oscillator. From the datasheet:
"HIGHER FEEDBACK RESISTOR GAIN OPERATION
The ADA4898-1/ADA4898-2 schematic for the noninverting
gain configuration shown in Figure 45 is nearly a textbook
example. The only exception is the feedback capacitor in
parallel with the feedback resistor, RF, but this capacitor is
recommended only when using a large RF value (>300 Ω).
Figure 46 shows the difference between using a 100 Ω resistor
and a 1 kΩ feedback resistor. Due to the high input capacitance in
the ADA4898-1/ADA4898-2 when using a higher feedback
resistor, more peaking appears in the closed-loop gain"
Is it general purpose... well no (curent noise is high and it is a tad too fast to be bullet proof). But, its no more general purpose than the AD797 which everyone loves.
Best, Sandro
Nice looking opamp, looks quite similar to the AD797 but with more slew rate, have you compared both of them? its optimum source impedance is around 375 Ohm, it may work as Mic preamp.
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