Small current generating circuit that can obtain UA level current - Power Circuit - Circuit Diagram
Circuit function
A constant current source is a circuit that provides a constant current when the load resistance changes, and is often used to measure resistance or impedance values. This circuit is suitable for weak current circuits. It uses J-FET as the current control component. The circuit composition is very simple, and a high-performance constant current source (called current source because current has no output) can be obtained.
Circuit working principle
The working principle of the circuit: It is easy to understand that +VCC is regarded as the reference voltage. If operating near the in-phase input range of the OP amplifier, the circuit will be unstable, so a level shift of approximately 2V is performed with Zener diode D2.
The OP amplifier A1 is an error amplifying circuit, and its function is to make the reference voltage VR after the voltage division of VR1 equal to the voltage generated across RZ, and to change the reference voltage, the constant current value can be arbitrarily set. The maximum current is determined by R2. When IO=1UA, R2=1.2/10 -8 power = 1.2M, R2 can be set according to requirements. If the current value becomes smaller, the input bias current IB of A1 will cause an error. Therefore, an OP amplifier with a small IB value should be selected.
Transparent Led Screen,Transparent Led,Led Transparent,Led Transparent Screen
Shenzhen Apexls Optoelectronic Co., Ltd , https://www.apexls-display.com