Current source in electronic circuits

Current source in electronics circuit and types of current source in electronics

1. Current Source Anil Rajpurohit June 20 th , 2021 1

2. SOURCES 2 A Source is a device which converts mechanical, chemical, thermal or some other form of energy into electrical energy The various types of sources available in the electrical network are voltage source and current sources.

3. What is current ? 3 Current source current source  is a two-terminal circuit element which supplies the same current to any load resistance connected across its terminals. The current source has a forcing function of current. Symbolic representation

4. Ideal Current Source 4 Ideal current sources are those sources that supply constant current to the load irrespective of their impedance. That means, whatever may be the load impedance; ideal current source always gives same current through it. R internal  = 0, the current source is short-circuited. When the parallel resistance is very high or infinite, R internal  ≈ ∞, the current source can be modelled as ideal. Ideal current sources supply constant current to the load irrespective of their impedance.

5. Practical current source 5 A  practical current source  is represented as an ideal current source connected with the resistance in parallel. Due to this internal resistance; voltage drop takes place, and it causes the terminal voltage to reduce. The smaller is the internal resistance (r) of a voltage source, the more closer it is to an Ideal Source.

6. 6 Example to understand internal resistance Value

7. 7 I Internal = R L /( R internal + R L ) X I Source I L= ( 250/(500+250) X3 I L= 1A I L = ( R Internal/( R L+ R Internal) X I Source I L= x ( 500/(250+500) x3 I L= 2A I Source = I Internal = 5mA R Internal =500Ohm V AB= V Internal = I Source X R Internal V AB= V Internal =3 X500=1500V or 1.5KW R T = ( R internal X R L )/( R internal + R L ) R T = (500 x250)/(500+250)=166.7 Ohm V AB= I Source X R T =3 X166.7 =500V Open Circuit or when no load Circuit with load RL V AB

8. Voltage controlled current source ( VCCS) 8 VCCS, maintains an output current, I OUT  that is proportional to the controlling input voltage, V IN . VCCS output current is defined by the following equation: I OUT  = αV IN . This multiplying constant  α  (alpha) has the SI units of mhos, ℧ α = I OUT /V IN , and its units amperes/volt.

9. Current controlled current source 9  it maintains an output current that is proportional to a controlling input current. output current “depends” on the value of the input current.  output current for a CCCS element is determined by the following equation: I OUT  = βI IN .    β  is a dimensionless scaling factor as β = I OUT /I IN , so therefore its units would be amperes/amperes.

10. Thank you 10