surianova
Joined: 01 Sep 2004
Posts: 399
Helped: 20
Location: ASIA
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 30 Dec 2004 3:57 Liming amplifier |
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Hi all,
I have design the limiting amplifier. As we know, the LA will amplifier the signal until at one time , the signal will be clip. My clip signal is at high 1.8v and low 0.6v with the power supply 1.8v. But when the signal clip at 0.6v, actually the input transistor and even the tail transistor is working in linear region. The LA is a simple diffrential structure with resistor as the load. My question is the tail transistor is in linear regoin, it will lower down the output impedence of the tail and will cause the CMRR become low. This is bad for the circuit.
But as i think back, when the is clipping at that stage or after another stage, actually it is working in attenuation stage and not the gain stage , that why i think that the CMRR is not important in this case because at this stage the commom noise cannot be amplify and it is ok for the tail transistor to work in linear region when the singal is clip. Am i rite? Got other opinoin are welcome. Thanks
Suria
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