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# 38 What is the node voltage method?

Node voltage node voltage method is based on the independent circuit variables as circuit analysis methods. Choose a node in the circuit as a reference node, and 38 datasheet and the remaining nodes and 38 price and the voltage between the reference point called the node that corresponds to the voltage. Polarity of the voltage reference node are nodes corresponding to positive polarity side of the reference node for the negative side. With the curse of the circuit nodes, the node voltage method is (n-1) independent node node voltage solution variables, and 38 suppliers and independent of the node list with KCL node voltage with the expression of the branch current equation.

39. What is diffusion? What is the drift movement?

diffusion: the material is always the direction from high concentration to low concentration of local movements, such as poor concentration resulting motion is called diffusion.

the P-type semiconductor and N type semiconductor production together, they cross the interface, the two carriers a large concentration difference, which is bound to the P region of the hole diffusion region N, and this Meanwhile, N area of ??free electron diffusion to the P region.

drift movement: the electric field force, the carriers movement called the drift movement. Formed in the space charge region, including the electric field, the minority carrier drift motion, holes from the N-region move to the P region, while the free electrons from the P region to the N zone movement.

40. What is the Miller effect? What purpose?

in Figure l-3 (a), there is an impedance Z (S) of the passive circuit connected to the gain-K amplifier between the input and output.

Z (S) the voltage across

U. -U. = (K +1) Ui = Z (S) Ji

Korea on Figure l-3 (b) there

Ui = Z7 (S) Ji

If the map 1-3 in the two circuits from the port office appears to be equivalent, that is

Z7 (S) = Z (S) / (K +1)

Z (S )

(a) b)

Figure 1-3 Miller effect

This is called the Miller effect.

Miller effect has many applications. For example, if the current is to measure the internal resistance of ammeter as small as possible, but the internal resistance of an ammeter is not easy to do a small, two at a certain process conditions, the smaller the internal resistance of ammeter ammeter makes the sensitivity becomes lower. However, in Figure 1-3 (a) shows the circuit Z (S) to replace the meter, thus the equivalent series impedance in the branch can be as small as 1 / (1 + K). If the amplifier operational amplifier, the equivalent series impedance in the branch of a small to negligible proportions. In the RC integrator, the RC constant r = RC larger circuits closer to the ideal points, the higher accuracy, but the smaller the output amplitude (see Figure 1-5).

In other words, only when the RC / (1/cu) "1, the simple RC circuit can be seen as an integrator, RC bigger, higher precision integrator, but the smaller the amplitude of the output circuit .

while Figure l-5 (b) used in the integrator op amp form, a complete solution to this problem, which can also be used Miller
effect (Theorem) to explain. On Figure l-5 (c) in the circuit, in (1-1) (1 + K) C C and consider an alternative amplifier gain can be obtained:

Uo = r then iiKK CU, ( 1-3)

Clearly, in the case of the same RC ljcuRcl + K) ci "1 can be better met. Taking into account the amplifier gain K>,>

1. So

Although equation (1-4) and (1-3) exactly the same, but with op-amp integrator form The accuracy is much higher than the simple RC integrator formed components.

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