Why do we use Widlar current mirror?
Why do we use Widlar current mirror?
A Widlar current source is a modification of the basic two-transistor current mirror that incorporates an emitter degeneration resistor for only the output transistor, enabling the current source to generate low currents using only moderate resistor values.
What is the advantage of Widlar current source?
It allows you to generate a low output current without using high value resistors.
What is meant by current mirror?
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.
What are the types of current mirror?
Learn Analog Circuits: Types and Applications of Current Mirrors
- Basic mirror.
- Mirror with beta helper.
- Widlar current source.
- Wilson mirror.
What is the advantage of Widlar current source over basic BJT current source?
It has a higher compliance voltage compared with the basic two transistor current mirror circuit. Wilson current mirror circuit creates noise across the output. This is due to the feedback which raises output impedance and directly affect the collector current.
How Widlar current source is a good power supply sensitivity?
Supply sensitivity For a simple Widlar current source (Fig. 1) the sensitivity is approximately 0.5 [1]; thus the same 10% variation of power-supply results only in a 5% change of output current. This improvement can be taken even further with the threshold referenced current source.
What is a MOSFET current mirror?
The current mirror is an analog circuit that senses the reference current and generates the copy or number of copies of the reference current, with the same characteristics. The replicated current is as stable as the reference current source.
Why is Wilson’s current a mirror?
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. The structure is shown in figure 11.9.
Why are current mirror so named?
The current mirror circuit gains its name because it copies or mirrors the current flowing in one active device in another, keeping the output current constant regardless of loading. The current being mirrored can be a constant current, or it can be a varying signal dependent upon the requirement and hence the circuit.
How can I improve my current mirror?
There are several options to improve the output of Current Mirror Circuit. In one of the solution one or two transistors are added over the traditional two transistors design. Construction of those circuits uses emitter follower configuration to overcome the base current mismatch of the transistors.
How to find the output resistance of Widlar current mirror circuit?
The output resistance can be determined by applying Kirchoff’s law across the left ground to the R2, it is- Again, applying Kirchhoff’s voltage law across the R2 ground to the ground of Input current, Now, changing the value, final equation to derive the output resistance of Widlar Current Mirror circuit is
What is a Widlar circuit?
The Widlar circuit may be used with bipolar transistors, MOS transistors, and even vacuum tubes. An example application is the 741 operational amplifier, and Widlar used the circuit as a part in many designs. This circuit is named after its inventor, Bob Widlar, and was patented in 1967.
What is a Wilson current mirror?
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.
What is a Widlar current source?
The output transistor uses an emitter degeneration resistor to provide low currents across the output using only moderate resistor values. One of the popular application examples of Widlar current source is in the uA741 operational amplifier circuit. In the below image, a Widlar current source circuit is shown.