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Design >> Analog Design >> newbie question about a long-tailed pair limiter
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Message started by mmzaj on Jul 4^th, 2009, 1:53am

Title: newbie question about a long-tailed pair limiter
Post by mmzaj on Jul 4^th, 2009, 1:53am

Hi

i know that the Amp in the attachment is a long-tailed pair limiting Amp . but i'am having a hard time trying to figure out the role of the capacitors !! the Amp should be functioning in the switching mode - the designer says so - , but capacitors introduce a "decaying" output !!
also , is it a good small signal Amp , or should i expect only a square wave at the output ? a detailed analysis would be nice :)
btw , R2 is connected to a +12V Vcc .

Title: Re: newbie question about a long-tailed pair limiter
Post by buddypoor on Jul 4^th, 2009, 4:11am

As I have told you already, it is series connection of a common collector and a common base stage.
Two capacitors at the base of T2 represent the common base effect and the other both caps (together wth the small resistor) isolate the power supply rail from the circuit. The last capacitor couples the input signal.
Of course, it is a good small signal amplifier for signals within the quasi-linear region of the transistors.
For a detailed analysis you should use a text book and search for differential amplifier.