DIY Transistor Tester
30/12-2013
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
Power-switch
Enclosure
* 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 :)
Downloads:
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
