Zero state response, zero input response, free component, forced component
The response of a linear time-invariant circuit or system can be decomposed into: zero state response + zero input response. It can also be decomposed into free component (transient component) + forced component (steady component)
Kirchhoff’s current law The current
flowing into a node is equal to the current flowing out of that node
Kirchhoff's second law For
any circuit, the sum of the voltage drop and the voltage rise of the power supply is 0
Telegen's Theorem 1 The
sum of voltage multiplied by current is 0, which reflects the conservation of power, and the total power absorbed by the circuit is 0
Telegen's Theorem 2 For
a circuit network with the same topology, the sum of the product of the voltage of all branches in one circuit and the current of the corresponding branch in another circuit is 0
Thevenin's equivalent theorem
Linear one-port network with source, the external circuit can be equivalent to a voltage source series equivalent resistance
Voltage source: open circuit voltage U oc U_{oc}Uoc
Equivalent resistance:
1) Series-parallel method (applicable to passive)
2) External power supply method (independent source is set to 0, controlled source is reserved, and the applied voltage is divided by the current to obtain the equivalent resistance)
3) Open-circuit short-circuit method (independent source) Keep, divide the open circuit voltage by the short circuit current)
Norton's Theorem
Linear one-port network with source, external circuit can be equivalent to current source parallel equivalent resistance
What is an ideal op amp?
The input resistance is infinite, the output resistance is zero, and the magnification is infinite
Judgment of the order of the circuit
1) Write the dynamic equation of the circuit, look at the highest order term
2) Simple circuit, only inductance or capacitance, is a first-order circuit, both are second-order
3) The transfer function can be obtained from the frequency response
Determine the circuit components in the black box
1) Measure the voltage with a voltmeter and determine whether there is a power supply
2) Measure the resistance with an ohmmeter, the resistance may be infinite, there may be an internal open circuit or a diode; the resistance is zero, the circuit may be short-circuited or there is a diode; the resistance is a fixed value , There is a resistance
3) measure the size of the capacitance to judge whether there is a capacitance
Lumped parameter circuit and distributed parameter circuit
Lumped parameter circuit: the actual size of the circuit electrical device d<<wavelength of the circuit signal λ
distribution parameter: does not satisfy d<<λ