Hi guys. Do transistors require a minimum collector current to operate normally? Specifically, I want to use a transistor as a switch to control around 50uA. The transistor I have is a 2n2222. Basically, how low can you possibly go on a transistor's collector and base current?

 

Hi guys. Do transistors require a minimum collector current to operate normally? Specifically, I want to use a transistor as a switch to control around 50uA. The transistor I have is a 2n2222. Basically, how low can you possibly go on a transistor's collector and base current?

What sparked the idea that there is a minimum to be maintained? Water pipes at home, what is their minimum?

 

If you could post a schematic and that is more easy to discuss.

The base current Ib_mini = 1 mA, and the Ic =1 0 mA.
When the current flows through the base reach up to 1 mA then the Vce will be get into the saturation status, it is just like as switch, but it has about 0.1~0.2V drop voltage.

 

What sparked the idea that there is a minimum to be maintained? Water pipes at home, what is their minimum?

Water pipes don't (or at least shouldn't) leak but transistors do. The leakage must set an absolute minimum current at which the transistor is useful.

 

50uA is quite do-able for a small transistor like the 2N2222. Check the spec sheet for the typical leakage current "Icbo".

The leakage current will be greater with higher collector voltage and especially with higher temperature.

Actually just checked and is 0.01uA at 60V and 25deg C. Increases to 10uA at 125deg C.