DIY Transistor Tester

DIY Transistor Tester





Component List:

R1:     5.6 K Resistor * (See below, important)
R2:     560 R
R3:     12 K
R4:     15 K
R5:     100 R (Use 1% resistor if you have)
R6:     1 K
R7:     120 K
R8:     0R - Jumper Link / wire
R9:     10 K
R10:   4.7 K
R11:   560 R

POT:     20 turn trim-pot, 2K is ideal, but up to to 10K is ok. * (See below)

C1:   Between 10 and 100 uF, 12 V or higher
C2:   Between 10 and 100 uF, 12 V or higher

J1:   DPDT Switch (See schematic) (You might want to solder wires or a pin header to these pads)

ZD1:    3.3 V Zener Diode
D2:     Silicon Diode  (1N4004, 1N4007 or similar)
D3:     LED (Battery OK indication, I used a blue LED)
D4:     LED (Test OK indication, I used a green LED)

78L33:    Any 3.3 V Regulator (Check datasheet to confirm pin out !)

LM334-Z:    LM334-Z Current source

TL074:     TL074 Quad Opamp

Some sort of connector for the test-port (I used a 5-way female Molex)

2 Connectors for T+ and T- (I used binding-posts)

Wire + 3 Jumper links (marked on silkscreen as lines)

9 V battery + clip




* NOTE: You don't need the trim-pot. You can replace R1 with a 6.8 K 1% resistor, and put a jumper across the POT pads on the PCB.
If you include the trim-pot, you will have to calibrate the Transistor Tester, for this you will need a multimeter that can measure uA.
The accuracy without the pot, and R1 at 6.8 K is 3 % + the error introduced by the resistors R1 and R5, so, if you cannot measure the current with better accuracy, there is no reason to include the trim-pot :)





Board overview:           transistortester_3v3_overlay.pdf

Signal layer:                   transistortester_3v3_Signal_layer.pdf

Silkscreen:                      transistortester_3v3_Silk.pdf

Silkscreen mirrored:    transistortester_3v3_Silk_mirrored.pdf

Schematic:                    sch_transistortester.png