One: Dynatron shoots class enlarge circuit in all

 

Dynatron shoots class amplifier in all is the most commonly used amplifier circuit, shoot class to magnify circuit is as follows in all:

 

 

By lecture of series of imitate circuit design the high frequency and equivalent model of 12 knowable dynatron is as follows:

 

 

According to circuit the principle can get voltage node equation:

 

 

Among them:

 

 

Can reach by above:

 

 

1) the first GmRL is volts d.c. gain

 

2) the 2nd is the voltage attenuation that brings by RΠ , Rx and Rs (cent is pressed)

 

3) this is passed contain right half plane at 0 o’clock, frequency dot is located in Gm ／ Cμ , frequency of this frequency place is very tall, be more than the WT of dynatron far, because we are negligible in this analysis process this is high frequency at 0 o’clock

 

4) pass from this contain knowable should pass contain two the limit

 

2: Shoot model of equivalent of only the limit of class enlarge circuit in all

 

Oversight is right half plane is high frequency at 0 o’clock, restrict by the bandwidth of dynatron additionally, can get dynatron shoots class to magnify model of equivalent of circuit only the limit is as follows in all:

 

 

Among them Cμ was magnified 1 ＋ (＇ of Gm ＋ Gs) RL times, that is to say the feedback capacitance between input and output was magnified 1 ＋ (＇ of Gm ＋ Gs) RL times, this is Miller effect.

 

 

3: What rice straps effect is farther discuss

 

If pursue (A) , capacitance Cf crosses a bound to turn over enlarge circuit at losing feedback two end, amplifier gain (enlarge multiple) for – A.

 

 

By the graph (B) , we can beg the input impedance that gives this amplifier:
 

 

The 1 ＋ A that because the negative feedback effect of this amplifier makes,the input capacitance of amplifier is feedback capacitance times, a is the gain of amplifier, this is famous Miller effect.