Circuit function
The current absorbing circuit is a circuit that absorbs a constant current from a voltage-applied load, and maintains a stable current even if the load voltage fluctuates. This circuit itself does not have a reference voltage and needs to be input from the outside. The constant current is controlled by the voltage EIN. It can be used as a current source for automatic measurements such as the light output or output current characteristics of the forward current of LEDs and photointerrupters.
Circuit working principle
The voltages at the two inputs of the OP amplifier A1 are controlled to make the bases equal. The voltage generated across the current sensing resistor R3 is IO.R3, and the voltage is compared with the control voltage EIN. If EIN>IO.R3, the A1 output potential is increased by IO.
The FET connected to the current control transistor TR2 for Darlington is used to cancel the error caused by the TR2 base current, and the base current flows from the collector through the FET.
Since EIN=0~1.0V, IO=0~10MA, so R3=EIN/=100Ω.
Application note
If the load voltage is low and the sense voltage generated by R3 is relatively large, then the output transistor cannot be properly controlled after it is saturated. In order to increase the output current, if the Darlington connection is used, the power tube can be connected to the TR2 for the test of the power circuit load. TR1 can be omitted when the current sink is large and the accuracy is not high.
Opzv Battery,Opzv1000 2V1000Ah Solar Battery,Solar Batteries 2V Opzv,Deep Cycle Battery 2V 1000Ah
Jiangsu Stark New Energy Co.,Ltd , https://www.stark-newenergy.com