This handy current-source circuit becomes even better when you realize how flexible it is. At this point we are ignoring channel-length modulation; consequently, as indicated by the equation, the drain current is not affected by the drain-to-source voltage.Classic Circuits You Should Know: Constant Current Source
Learn about a straightforward version of a circuit that is essential in the design of analog integrated circuits. It is possible to make an active constant current source using a single transistor, although more comprehensive designs are also available using additional components. Supporting Information Bipolar Junction Transistors: A constant current source is a power generator whose internal resistance is very high compared with the load resistance it is giving power to.
This voltage is labeled V CS , meaning the voltage across the c urrent- s ource component; this helps to remind us that Q 2 , like any well-behaved current source, generates a bias current that is not affected by the voltage across its terminals. Look at the following current divider circuit below: Also stand-alone current sources are also needed in processes ranging including electrochemistry and electrophoresis.
Since the load has infinite internal resistance, current will always seek to escape from it to a lower resistance path. Load More Articles. Arfy ;o 2018-04-05.
Even better, each of these currents can be different—they can be individually modified simply by adjusting the width-to-length ratios. The culprit is channel-length modulation. This is because they are used 1 for biasing and 2 as active loads.
They may also be used as wide voltage range pull-up links within power supplies and other wide voltage range circuits. You can see that the current is constant all throughout despite changes in voltage or resistance.
Now let's increase the resistance again. What is Bias Voltage? Often these constant current sources use transistors, although FETs and where applicable, vacuum tunes of thermionic valves can be used as well.
Nevertheless they can still be used just as effectively. Now let's increase the difference in resistances between the two resistors, so that the current division is even more pronounce.