r t norton equivalent circuits (诺顿等效电路)

Source Transformations Source Transformations: 一我們可以將一個電壓源串聯一電阻的電路由諾頓等效電路取代(或反之)。 Source Transformation 為外部等效(external equivalence)非內部等效。 Source Transformations If nodes a & b are open External equivalence Source Transformation 要注意電流源、電壓源方向(以維持等效)。 Source Transformations If nodes a & b are open Not internal equivalence Source Transformations 如何由外部估測是否有諾頓(Norton)等效? 諾頓等效會持續作工(發熱) P=i2R, i≠0 Example 2.20 Source Transformations Maximum Power Transfer 一個兩端電路外接一負載電阻，負載電阻值為何其所消耗功率(maximum power )最大？ Maximum Power Example 2.21 Find the load resistance for maximum power transformation 2.7 SUPERPOSITION PRINCIPLE (疊加原理) The superposition principle states that the total response is the sum of the responses to each of the independent sources acting individually. In equation form, this is 2.7 SUPERPOSITION PRINCIPLE (疊加原理) 要獲得某一 independent source 所造成的response，則將其他 independent source zeroing (reduce the source value to zero)。 Suppose the response is the voltage across Suppose the response is the voltage across Linearity Ohm’s law is a linear equation. The controlled source ics=Kix is also a linear equation. Superposition principle does not apply to circuits that have element(s) described by nonlinear equation(s). Dependent source do not contribute a separate term to the total response. We must not zero dependent source in applying superposition。 However, dependent source affect the contributions of the independent sources. Example 2.22 Find 2.8 Wheatstone Bridge 惠斯登電橋測直流電阻 如同天平秤，以三個已知電阻量測一個未知電阻 。 平衡時， , vab=0. WHEATSTONE BRIDGE KCL node a KCL node b KVL upper loop KVL lower loop WHEATSTONE BRIDGE Example 2.23 If R1=1-kΩ, R3= 0~1100-Ω steps by 1-Ω R2: 1k, 10k, 100k or 1MΩ (a) What is the value of Rx such that the bridge is balanced with R3=732 Ω, R2=10k Ω? (b) What is the largest value of Rx for which bridge is balanced. Example 2.22 If R1=1-kΩ, R3= 0~1100-kΩsteps by 1-Ω R2: 1k, 10k, 100k or 1