Julian18
Full Member level 3
shunt feedback amplifier
Hi, there:
I am currentlly involved in a project of broad-band LNA, and the basic ckt is the shunt feedback amplifier, after reading some articles and papers, i find some authors assume the gain to be -(gm-1/Rf)/(1/Rf+1/Rl), or in case of large Rl, gain=(1-gm*Rf), where Rf is the feebback resistance, Rl is the load resistence and gm is the transconductance of the transistor. Using return ratio analysis, i can get the same result as the one mentioned above only when i assume Rs is approaching zero(which implies the feedback is not suffiicient), what is the problem here? can any one here give me a derivation for the gain of this amplifier
TIA.
Hi, there:
I am currentlly involved in a project of broad-band LNA, and the basic ckt is the shunt feedback amplifier, after reading some articles and papers, i find some authors assume the gain to be -(gm-1/Rf)/(1/Rf+1/Rl), or in case of large Rl, gain=(1-gm*Rf), where Rf is the feebback resistance, Rl is the load resistence and gm is the transconductance of the transistor. Using return ratio analysis, i can get the same result as the one mentioned above only when i assume Rs is approaching zero(which implies the feedback is not suffiicient), what is the problem here? can any one here give me a derivation for the gain of this amplifier
TIA.