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What is current mirror source?
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. Or it can consist of a current-controlled current source (CCCS).
What is the difference between current source and current mirror?
if the two pMOS are equal, they provide the same drain current to both the branches: suppose that Vbias is chosen so that the drain current will have a certain (constant) value Ibias.
Which current mirror provides the most constant current source or sink?
Wilson current mirror
11.7. A Wilson current mirror or Wilson current source, named after George Wilson, is an improved mirror circuit configuration designed to provide a more constant current source or sink. It provides a much more accurate input to output current gain.
Why we use cascode current mirror?
Advantages: 1. Cascode current mirror eliminates the channel length modulation effect by keeping Vds1 = Vds2 constant in the ratio: Iout = (W/L) (1+λVds2 ) (W/L) (1+λVds1) 2. Improves output resistance.
Why is the current of a mirror greater than zero?
Parameter β 0 is the transistor β-value for VCB = 0 V. If V BC is greater than zero in output transistor Q 2, the collector current in Q 2 will be somewhat larger than for Q 1 due to the Early effect. In other words, the mirror has a finite output (or Norton) resistance given by the ro of the output transistor, namely:
How is the drain current of a mirror determined?
The drain current of a MOSFET ID is a function of both the gate-source voltage and the drain-to-gate voltage of the MOSFET given by ID = f ( VGS, VDG ), a relationship derived from the functionality of the MOSFET device. In the case of transistor M1 of the mirror, ID = IREF.
What kind of mirror reverses the current direction?
Conceptually, an ideal current mirror is simply an ideal inverting current amplifier that reverses the current direction as well. Or it can consist of a current-controlled current source (CCCS).
Can a current mirror be approximated by a Norton impedance?
For small-signal analysis the current mirror can be approximated by its equivalent Norton impedance . In large-signal hand analysis, a current mirror is usually and simply approximated by an ideal current source. However, an ideal current source is unrealistic in several respects: