Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
The desirable property of common base is that the base-collector capacitance goes from the output to ground and does not cause a miller effect or feedback that causes oscillations. The collector-emitter capacitance is much smaller. In the early days of large junction areas the common base circuit was commonly used at VHF.
Modern transistors have much smaller capacitances and so the common emitter is used more frequently because of its higher gain.
hi, thank you for the reply..
what is the miller effect? is it the miller effect is the feedback that cause oscillation? so what will happen if it caused oscillation? is it reduce the gain? why?
hi.. thank you for the answer... but i still not got it, what is the input-output capasitance? is it the capasitance of the coupling capasitor? why it reduces the bandwidht in high frequency in Common Emitter but not in Common Base?
The desirable property of common base is that the base-collector capacitance goes from the output to ground and does not cause a miller effect or feedback that causes oscillations. The collector-emitter capacitance is much smaller
hai flatulent if miller effect is hindrance for high frequency operation,then i think that we can easily migrate to CB and also to CC.ie Both CB nad CC can be called as high freq.amplifier.(no miller effect in CB,CC amp)
reply me abt the my conclusion that absence of miller effect make CC as high freq. amp
The miller effect is always present. It is just that the CB takes advantage of the low collector-emitter capacitance for bandwidth and for stability purposes. The CC has a gain of nearly +1 which makes the miller capacitance less than the base-emitter capacitance. The base-collector capacitance does not get multuplied.
In the early days it was common to have the RF amplifier of a VHF receiver be CB. The CB is used as the second stage of a cascode.
The other disadvantages with CB and CC make them less desirable these days compared to CE because the base-collector capacitances are small in modern transistors.
In the early days the manufacturing methods had 20-100 or more micron geometries.
A cascade of CB or CC stages produces no more power gain than one stage unless you use tranformer coupling.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
