Calculates the root mean square Noise Voltages VN(rms) at the OUTPUT of a single stage Common Emitter amplifier based on the a.c. model opposite and input variables entered ~ The focus is on the amplifier Noise Figure [NF] and Signal to Noise Ratio [SNR] for a given input signal VS ~ Additional results in nV/√Hz are the respective noise voltages in a 1Hz bandwidth
It does not take into account flicker noise and assumes perfect resistive loads and modern silicon transistors with low noise bias and the transistor gain [β] remains constant within the measurement bandwidth [Bn] defined
The circled nodes B C and E represent the external connections of the transistor and lower case rbb and re are internal but also in series with B and E respectively ~ Collector or output resistance ro is not used here but can be added parallel with RC and will reduce the gain along with the output noise
Simply referring only the transistor noise to the input does not give the full picture for a common emitter or common base amplifier where base and collector shot noise cancellation can occur ~ Also some of the formulae found in even the best reference and often repeated assume that β ≫ 1 and re ≥ rbb which for low source resistance designs is not always the case ~ Click here for other calculators
There are a lot of outputs and although this looks confusing at first it is advantageous to have all these intermediate answers readily available and gives an insight to what effect the input changes have on the gain and input impedance and noise from each source ~ Start by entering your Collector Current
See these references:
The Art of Electronics 3rd edition chapter 8 ~ By Paul Horowitz and Winfield Hill
Noise in Transistor Circuits ~ By P. J. Baxandall ~ Wireless World November 1968
Designing low–noise audio amplifiers ~ By Wilfried Adam ~ Wireless World June 1989
Introduction to low–noise amplifier design ~ By A. Foord ~ Wireless World April 1981
The design of Low-noise audio frequency amplifiers ~ By E. A. Faulkner ~ The Radio and Electronic Engineer July 1968 ~ This article along with the book 'Low-Noise Electronic System Design' By C. D. Motchenbacher and J. A. Connelly should answer most questions about electronic noise
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" Do you work it out one by one ~ Or played in combination "