Hi everyone,

Would you please help me to design a constant current source. The range for R_load should be between 15 ohm to less than 150 ohm. Current source of about 1mA is sufficient. The frequency of the voltage source is 500 Hz.

Thanks for your help....

 

AC is by definition not constant current.

 

As the voltage across 150 ohms with your 1 mA of current is only 150 mV then a resistor of 15K from a constant voltage 15 volts 500 hz source would give you a pretty good approximation of a constant current source. It would vary by about 1% over your range of load resistors.

Les.

 

Would you please help me to design a constant current source. The range for R_load should be between 15 ohm to less than 150 ohm. Current source of about 1mA is sufficient. The frequency of the voltage source is 500 Hz.

Another approach would probably be a circuit commonly known as a "Howland current pump" or "Howland current source." This paper will tell you all you need to know to design one suited to your needs.

AC is by definition not constant current.

Wrong.

In one very narrow, trivial sense you're not incorrect: in AC, the instantaneous values of voltage and current do change with time. But invariance of current over time is NOT what we are referring to when we use the term "constant current source": we mean a current source whose output current is independent of load impedance. And a constant current source can be AC just as well as DC.

 

Sounds like an audio power amplifier to me.

 

Sounds like an audio power amplifier to me.

Audio amplifiers are normally constant voltage, not constant current.

 

And they also put out a LOT more than 1 mA.