Determination of the show-stopper values of feedback elements

Exercise

The figure below shows a concept of a negative feedback voltage amplifier with resistive feedback. The amplifier is driven from a voltage source with a source resistance \(R_s=600\Omega\). The voltage gain of this amplifier should be 20dB, while its noise figure should be better than 2dB.

Give the maximum value of the feedback resistors.

Concept of a negative feedback voltage amplifier

Fig. 11 Concept of a negative feedback voltage amplifier.

Hint

The maximum value of the feedback resistors is determined by their noise contribution. This contribution should not result in a noise figure larger than 2 dB.