Hi, Can anyone help me check the circuit and if possible tell me what could be the problems? At 12V supply,the circuit works fine and I am getting approx 60mA with resistance 100 ohms. Now I wanted to increase the current by reducing the resistance to 50 ohms.And I got 115mA. Since there isnt much resistance to reduce,I thought of increasing the current by raising the voltage to 24V. Strangely the current only increase by 1 to 2 mA and the npn transitor gets hot with some burning smell. The npn transistor 2SD1857A has a high reverse voltage Vcbo,vceo at 160V.I have no idea why the transistor heat up but no significant increase of current to my LED. Furthermore,at 12V supply,the vce is about 5V.But as I increase the Vs,the Vce keeps increasing. So my question is, 1)Why the transistor heated up but there was no increase in current when the supply raised from 12V to 24V. 2)Some of my transistor has very low VCE when current is applied at the base but this transistor has a high VCE.What is the parameter that affects the VCE?I think the VCE suppose to be low when current applied at base. Thank you.