Contents
Where are current mirror used?
The current mirror is used to provide bias currents and active loads to circuits. It can also be used to model a more realistic current source (since ideal current sources don’t exist). The circuit topology covered here is one that appears in many monolithic ICs.
What are some real uses for a multi transistor current mirrors?
Current mirrors are frequently used in linear integrated circuits such as op amps. They are used to provide a stable current for biasing transistors and transistor pairs such as differential pairs.
What are the types of current mirrors?
This article briefly reviewed BJT operation, then it explored four types of BJT current mirrors: the basic mirror, the mirror with beta helper, the Widlar current source, and the Wilson mirror.
How do you make a current mirror?
The first trick to use bipolar junction transistor as a current mirror circuit is to construct an exponential voltage to current converter using the transistor. This is done by providing a voltage across the base-emitter junction of the BJT and the collector current is taken as an output.
What is cascode mirror?
Cascode current mirror eliminates the channel length modulation effect by keeping Vds1 = Vds2 constant in the ratio: Current becomes constant for quite large value of Vds e.g. in this case minimum Vds is 1.2 V. 3. Body effect is also present which disturbs the output current.
Why cascode current mirrors are used?
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.
What are the drawbacks of basic current mirror?
Drawbacks of Basic current mirror In Basic CM , we have neglected channel modulation. CLM effects result in significant error. ∴ to suppress effect of CLM, cascode CM is used.
What is the drawback of a current mirror circuit?
1) The mirror adds noise. This is worst if there are no emmitter resistors. With big enough emmitter resistors, the noise can be reduced to an insignificant level. 2) The mirror may add distortion.
How are current mirrors used in real life?
Current mirrors are frequently used in linear integrated circuits such as op amps. They are used to provide a stable current for biasing transistors and transistor pairs such as differential pairs. I saw a real life use of a discrete current mirror a couple of months ago in this question.
What are the two types of current mirror circuits?
Current mirror circuits may be found in two basic varieties: the current sinking configuration, where the regulating transistor connects the load to the ground; and the current sourcing configuration, where the regulating transistor connects the load to the positive terminal of the DC power supply.
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:
Can a current mirror be slaved from more than one voltage?
Multiple current mirrors may be slaved from a single (Q1 – Rbias) voltage source. Note that it is customary to draw the base voltage line right through the transistor symbols for multiple current mirrors! Or in the case of Q4 in the figure above, two current sources are associated with a single transistor symbol.