how to improve SFDR of an amplifier

[kudret]

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...

 

[Audioguru]

-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.

 

[godfreyl]

My professor told me to design a three stage audio amplifier with 105dB SFDR at 10kHz.

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?

Are there any methods to improve SFDR?

To reduce distortion, you need to improve the inherent linearity of the circuit and/or apply more negative feedback.

 

[kudret]

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?

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.