About the article

Transistor Curve Tracer

On USB, for bipolar trannies and FETs

Based on a Labs project | April 2012 | Find it here
Transistor Curve Tracer
This practical instrument can be used to measure and record the characteristic curves of NPN and PNP bipolar transistors, N- and P-channel JFETs, and N- and P-channel MOSFETs. The circuit is based on an R8C/13 microcontroller, which transfers the measurement data to a Windows application program via USB.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info / Update

Quick Project Specs
- R8C/13 microcontroller control module
- PC link via USB port
- User-friendly PC program with Help function (runs under Windows 2000 and XP)
- Curve data can be exported to and imported from Excel
- Checking transistor matching
- Records characteristic curves of NPN and PNP transistors, N-channel and P-channel MOSFETs, and N-channel and P-channel JFETs
- Plotted curves can be printed out or embedded in other applications



  • The circuit diagram does not show the link between pin 11 of K1 and pin 22 of the R8C/13 module. The PCB for the project is not affected.

  • In the circuit diagram (Figure 2, section a), the bussed connection between pin 22 (P3.0) of the R8C/13 module and resistor R24 is missing. This connection is however present on the circuit board, for which no modification is required.

  • In the component list, transistor T2 should be a type BC557A, not BC547A. No modification is required to the PCB or the schematic.

Component list
Controller board # 080068-2
R1 = 1kO5, SMD 0603
R2,R3 = 27O, SMD 0603
R4,R10,R11,R14-R28 = 470O, SMD 0603
R5,R6,R7 = 220kO, SMD 0603
R8,R9,R12,R29,R30,R31 = 4kO7, SMD 0603
R13 = 1kO, SMD 0603
C1,C2,C4,C8,C9,C11,C13 = 100nF, SMD 0603
C3,C12 = 22pF, SMD 0603
C5,C6 = 10pF, SMD 0603
C7,C10 =10µF 25V, SMD case A
D1 = LL4148
D2 = LED, 3mm, low-current
IC1 = PL2303X
IC2 = R5F21134FP (R8C/13)
K2 = USB-B socket
K1 = 20-way (2x10) DIL pinheader
S1 = pushbutton, 6mm, SMD
X1 = 20 MHz quartz crystal, SMD
X2 = 12 MHz quartz crystal, SMD
JP1 = 2-way SIL pinheader with jumper
F1 = 100 mA Polyfuse

Main board # 080068-1
R1-R18,R24-R33,R37,R38,R41-R45,R48,R51,R52,R53 = 10kO
R19,R20,R22 = 4kO7
R21 = 931kO
R23 = 88kO7
R34,R35 = 1O5
R36 = 100O
R39,R40,R46,R47 = 20kO
R49 = 1O 1W
R50 = 90kO9
C1,C2 = 2200µF 35V radial
C3-C6,C11,C12,C14-C17,C19-C35 = 100nF, lead pitch 2.5mm
C7-C10 = 10µF 25V radial
C13,C18 = 47nF, lead pitch 2.5mm
C36,C37 = 22nF, lead pitch 2.5mm
D1-D4,D6,D7 = 1N4148
D5,D8 = 5.6 V 500 mW zener diode
D9-D12 = LED, low-current, 3 mm
B1 = VM18, bridge rectifier 1 A / 100 V, DIP4
T1,T2 = BC547A
T3 = BD139
T4 = BD140
IC1 = 7812
IC2 = 7815
IC3 = 7915
IC4 = 7912
IC5,IC6,IC8,IC11,IC12 = TL082P
IC7,IC9 = DG441DJ
IC10, IC13 = TL081P
K1 = 20-way DIL socket
K2 = 3-way PCB terminal block, lead pitch 2.5mm
F1 = 100 mAT (slow) glass fuse, with holder
TR1 = mains transformer, secondary 2x 15V / 14VA
4 heatsinks type FK218/SA32 (21 K/W)
Microcontroller and PC Software: free download 080068-11.zip at [3].
PCBs 080068-1 and 080068-2, available from the Elektor Shop.
Controller board also with components fitted, Elektor Shop # 080068-91.
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