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Laboratory voltage and current source

After a long time, I decided to do some new design and because I did not have some regulated current source in my lab, I decided to do it. After a while on the Internet, I discovered a source that would match my requirements, so the current can be controlled from 2mA to 4A, which is sufficient for most applications, and the voltage can be controlled from zero to 30V. This power supply is very good up to 30V (or a little less, due to losses on rectifier diodes ..) when the voltage drop at 4A is maximum 1V. To this source I have heard more negative than positive, the reason why someone burns or oscillates is countless, but if the process is accurate and the component values ​​are in tolerance, the source should not be a problem. However, I recommend to increase the values ​​of the suppressor caps that prevent operational amplifiers from oscillating. If you do, the problem should not be. As the final power transistor, here is, according to the original scheme, used 2N3055, but it is possible and I recommend to use KD503,501 ... because maybe in the GM 2N3055 they are sold as National Semiconductor imitations that last 1/10 of the reported current. And then it can be used instead of 2N2219, which is before power, can be replaced by KF506. Otherwise, all components can be purchased normally and the price does not exceed 250Kč (without potentiometers and power transistor) power transistor can be easily found in old TVs (of course I mean KDčka ..) as well as filter capacitors. The source is initially built at 3A, but it also manages 4A when R7 is reduced. Then I also used two end transistors in parallel ...



R1 = 2,2 KOhm 1W
R2 = 82 Ohm 1/4W
R3 = 220 Ohm 1/4W
R4 = 4,7 KOhm 1/4W
R5, R6, R13, R20, R21 = 10 KOhm 1/4W
R7 = 0,47 Ohm 5W
R8, R11 = 27 KOhm 1/4W
R9, R19 = 2,2 KOhm 1/4W
R10 = 270 KOhm 1/4W
R12, R18 = 56KOhm 1/4W
R14 = 1,5 KOhm 1/4W
R15, R16 = 1 KOhm 1/4W
R17 = 33 Ohm 1/4W
R22 = 3,9 KOhm 1/4W
RV1 = 100K trimmer
P1, P2 = 10KOhm/lin
C1 = 3300 uF/50V electrolytic - lepší je víc
C2, C3 = 47uF/50V electrolytic
C4 = 100nF polyester
C5 = 200nF polyester
C6 = 100pF ceramic
C7 = 10uF/50V electrolytic
C8 = 330pF ceramic
C9 = 100pF ceramic
D1, D2, D3, D4 = 1N5402
D5, D6 = 1N4148
D7, D8 = 5,6V Zenerka 2W
D9, D10 = 1N4148
D11 = 1N4001 diode 1A
Q1 =BC547(BC548)
Q2 = 2N2219 NPN nebo KF506
Q3 = BC557(BC327)
Q4 =KD506(501), (2N3055)
U1, U2, U3 = TL081
D12 = červená difůzní ledka


As I have a habit, the source I appropriately "miniature" and miniaturized as much as possible :-), instead of ceramic caps I gave better quality and more stable foil, precision IO sockets, high-quality wires and precision potentiometers, toroid.
During the development, I came across a 20-year-old aluminum construction box on Aukra, and as is well known, it is better and better processed than today's China boxes! I also thought about what to do with the quantity indicators. I programmed using the USBasp programmer for ATMELy and AVR eXtreme Burner. It works great, but there is a smaller snag and the fact that the ATMEL legs must be soldered to the cap (10nF) between pins 22 and 21, otherwise the reference voltage oscillates and the whole is unstable. the menu must be pressed and the power on. It all worked out for about 2000CZK. ,, Well enough talk, in case of questions contact me at admin@martiname.cz ... and now some photo from construction. Here's the PCB.