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A current mirror is a circuit designed to copy a current through one active device by controlling the current in another active device of a circuit, keeping the output current constant regardless of loading. The current being "copied" can be, and sometimes is, a varying signal current.
To design the mirror, the output current must be related to the two resistor values R 1 and R 2. A basic observation is that the output transistor is in active mode only so long as its collector-base voltage is non-zero. Thus, the simplest bias condition for design of the mirror sets the applied voltage V A to equal the base voltage V B.
The principal limitation on the use of the Wilson current mirror in MOS circuits is the high minimum voltages between the ground connection in Fig. 5 and the input and output nodes that are required for proper operation of all transistors in saturation. [10]
The simplest non-ideal current source consists of a voltage source in series with a resistor. The amount of current available from such a source is given by the ratio of the voltage across the voltage source to the resistance of the resistor (Ohm's law; I = V/R).
Most commonly the active load is the output part of a current mirror [1] and is represented in an idealized manner as a current source. Usually, it is only a constant-current resistor that is a part of the whole current source including a constant voltage source as well (the power supply V CC on the figures below).
Transistors Q11 and Q10 form a Widlar current mirror, with quiescent current in Q10 i 10 such that ln(i 11 / i 10) = i 10 × 5 kΩ / 28 mV, where 5 kΩ represents the emitter resistor of Q10, and 28 mV is V T, the thermal voltage at room temperature. In this case i 10 ≈ 20 μA.
The maximum load is the one that draws the greatest current, i.e. the lowest specified load resistance (never short circuit); is the voltage at minimum load. The minimum load is the one that draws the least current, i.e. the highest specified load resistance (possibly open circuit for some types of linear supplies, usually limited by pass ...
A resistor–inductor circuit (RL circuit), or RL filter or RL network, is an electric circuit composed of resistors and inductors driven by a voltage or current source. [1] A first-order RL circuit is composed of one resistor and one inductor, either in series driven by a voltage source or in parallel driven by a current source.