LM334Z Testing Circuit
Hello everyone, I hope you have a good day.
In this project I will show you How to test functionality of LM334Z Current Source IC. You can simply testing this circuit for understand how basic current source ic's work.
Supplies
Introduction
Before we test LM334Z constant current source device we need to know what is current source device ? and which applications uses this ?
What is Current Source Device ?
Simply, current source device is integrated circuit that provides constant current on its output. These integrated circuits require minimal additional design with external components (such as resistors or capacitors) to provide a stable current. The purpose of these integrated circuits is maintain a specific current regardless of changes in the voltage across the load.
Applications
LED Drivers: Constant current is essential to ensure consistent brightness in LEDs.
Battery Charging: Lithium-ion and other types of batteries require a stable current during charging.
Sensors: Some precision sensors need a constant current for accurate measurements.
Test and Measurement Systems: Stable current sources are crucial for testing sensitive devices.
In summary, if you need a stable and precise current in a circuit, constant current source ICs can provide an solution.
Circuit Diagram
If we want to test functionality of LM334Z current source we need to firstly create an test circuit as shown in the figures. After we created this circuit we will try to understand how LM334Z and this circuit works
Testing & Result
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By examining the LM334Z datasheet, we have reached the following conclusions:
The LM334Z is an adjustable current source integrated circuit. In this project, we used the TO-92 package version, which has 3 pins.
V+, R, and V- (The pin diagram is provided in the figures used in this project and in the datasheet.)
A maximum voltage of 40V can be applied from V+ to V-.
It consumes maximum 400mW power.
A constant output can be adjusted in the range of 1µA to 10mA.
Using these information, we will perform the test utilizing the Basic 2-Terminal Source circuit provided in the datasheet.
If we use Basic 2-Terminal Source circuit (as shown in fig.) Iset (i.e constant current output) determined by 67.7 mV/RSET (@ 25°C) formula. This formula has been used as the basis for the circuit we built in this project.
In summary Iset (i.e constant current output ) approximately dividing 68 to Rset resistor value. Based on this, when we use 680 Ohm resistor (Rset) we will see as shown in figure 0.1mA (i.e 100uA) are seeing the result. Bam ! Constant current is ready !
The most important result of this test is the stability and steadiness of the current. The output current changes only when the Rset adjustment resistor is changed. Connecting a load or changing the source voltage must not affect the result. This creates a constant current that we can use in our projects.
Also this test improved with an diode and secondary resistor via building Zero Tempco circuit in datasheet.