Need constant current circuits

I need constant current for the following applications:
1. LNA FET with Vg and Vd: Need constant current for 10mA
2. Single power supply constant current +4V and 100mA
If an amplifier adopt the constant current circuits, how much the amplifier gain would vary at 0-50deg ambient temperature? My target is 0.2dB.

I think, the question demands for empirical measurements. According to manufacturer datasheet, that sometimes specify gain for different temperatures at constant Ids, I would expect a larger variation than just 0.2 dB. If so, you would need to apply an empirical Ids versus temperature curve to achieve constant gain.

Using constant current circuit do not guarantee that this will be stable vs temperature.
You need a temperature compensated bias circuit. Try to use a bandgap reference generator, which is temperature-independent circuit.