DC Analysis - Saturation

Thread Starter

Schniz2

Joined Apr 15, 2010
22
I need to complete a DC analysis of the attatched circuit, but i am not sure how to approach it because the transistor Q3 needs to operate in its saturation region for some of the input range. Is there a way to solve the Collector/Base currents of Q3 and Q4?
 

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t_n_k

Joined Mar 6, 2009
5,455
Were you given any other information - such as the transistor β values?

Q5 & Q6 (in part) form a current mirror which controls Q3 & Q4 emitter currents.
 

Thread Starter

Schniz2

Joined Apr 15, 2010
22
yep, im analysing for B=100.. ive changed my circuit design now... managed to make it out of a differential amplifier...
i still have one of the transistors operating in saturation though... how do you find R_be of a transitor when you only know the saturation currents.. you cant really use (n*V_T)/(I_B) because I_B is huge compared to what it would be in the linear region.... or does the value of R_be actually change when the transistor goes into saturation?
 
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