adjustable current booster

hi there, please help me, i want to boost the output current from an op amp which will vary from 0 - 32 V. i tried using 2n3055, i can boost the output current, and i can adjust the output current, but the output voltage would change if i change the output current, how to change the output current without change the output voltage?

thanks.

Hi Zhi_yi,

Simply include the 2N3055 in the feedback loop of the opamp.
In other words: move the feedback loop of the opamp from
the output of the opamp to the emitter of the 2N3055.

on1aag.

thanks..

on the first schematic, i use the pot 100k to udjust the output current at the emitter of the 2N3055 by changes the Ib. the output current can be adjusted from about 100mA to 1.5A, but the problem is if the input voltage (V1) is under 5V, the output voltage (emitter of 2N3055) changes to about 8 to 10 V. the input voltage (V1) = output voltage if the input voltage range from 10V to 20V, if the input voltage (V1) is above 20V, the output voltage would drop, for example, if the input voltage V1 is 32 V, the output voltage drop to 25V. please correct my circuit

on the second schematic, the output current can be boosted to about 3.5A, but the input voltage (V1) can't be same with the output voltage, please tell me how to correct it..

thank you very much

Take a look at the attached picture .. It shows the way of boosting the output current of an opamp with NPN and PNP transistors .. Maybe you should try that concept ..

BTW> Why do you use LM311??? It is not an opamp - it is a comparator - so, in linear applications it is rather useless ..

Regards,
IanP

thanks IanP,

sometimes ago i used lm324, but i have it damaged and i have run out of stock, and not yet bought a new one, i can't use 741 since i use 32V and 0V, so, for examine boosting the current, i tried using lm311 hehe.. from the circuit, if i want to make the output current adjustable, and my input voltage would be range from 0 V to 32 V with the interval 1mV. where should i add the potmeter? it's class B amplifier for gain the current.. thanks..