how to improve SFDR of an amplifier

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kudret

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Hi all,

it may be general question but I need some general knowledge. My professor told me to design a three stage audio amplifier with 105dB SFDR at 10kHz. The best SFDR value I was able to get from my other projects is 65dB at 1kHz. Are there any methods to improve SFDR?

thanks...
 

-105dB is almost 0.0005% and that is just the peak. The RMS value of the distortion will be less.
Some very good audio opamps have harmonic distortion at 1kHz of 0.00008% but with a 2k ohm load, a gain of 1 and an output level of 1vp-p.

You might be able to hear 0.1% distortion at 1kHz.
 

kudret said:
My professor told me to design a three stage audio amplifier with 105dB SFDR at 10kHz.
Click to expand...
What sort of amplifier? Power amp, microphone preamp, line-level preamp, something else?

What is the required gain, input impedance, load impedance, signal level etc etc?

kudret said:
Are there any methods to improve SFDR?
Click to expand...
To reduce distortion, you need to improve the inherent linearity of the circuit and/or apply more negative feedback.
 

godfreyl said:
What sort of amplifier? Power amp, microphone preamp, line-level preamp, something else?

What is the required gain, input impedance, load impedance, signal level etc etc?
Click to expand...

thanks for your reply

these are the specifications;

Single ended three stage audio amplifier.

SFDR > 105 dB at 10kHz
SNR > 100 dB at 20kHz
BW = 20kHz
Swing > 1Vpp
C load > 100pF
R load = 600 Ω
Idd < 10 mA

there is no more detail about specifications. This is just a one term project for the lesson, I guess prof does not care about gain or the sort of amplifier.
 

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