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Advantages of cascoded circuits?

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Student1990

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Hi,

I've just read in a book that a cascaded circuit has a high input and output resistance.

About this I have a two questions:

1) which advantages has a circuit with high input and output resistance?

2) why is a cascaded circuit useful for a circuits?

For every answer I will be thankful.

:smile:

Sarah
 

Dear Sarah
Hi
The cascaded amplifiers , will have good bandwidth and low THD .
And i don't think that the cascaded amplifiers have high input and out put resistance .
Good luck
Goldsmith
 

Hi Goldsmith,
thanks for your answer but it is not efficient.

Just now I've found out, that the gain of a simple cascaded circuits (common-source and common-gate) is gm*Rout.
It is desirable to increase the gain by maximizing Rout, which depends on conductance and resistance of CG transistor.

Now is my question: which disadvantages has a cascaded circuit?

thanks
Sarah
 

Don't confuse cascade with cascode!

Cascode is used to reduce Miller capacitance and possibly increase gain and improve bandwidth. Cascade is simply putting one stage after another to increase gain.

Keith.
 

Two disadvantages of additional amplifier stages: Increased power consumption, more noise generated.
 

If your mean is cascode ( as keith said ) , the miller effect will reduce . and the out put impedance will increase and input impedance will increase too . and it can work at very high frequencies. and you can use it at rf systems with cheap transistors ( as a high frequency pair ).
Best Wishes
Goldsmith
 

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