- on Test & Measurement
- Published in issue 3/2005 on page 0
Quick go/non-go testing for operational amplifiers
If you ever want to use an operational amplifier salvaged from an old circuit or from the junk box, you will take into account that the device may no longer work properly. Unfortunately, it is not as easy to perform a quick go/no-go test on an operational amplifier using a multimeter as it is with a resistor, coil, fuse, diode or even a capacitor. Although an opamp tester would obviously be a useful thing to have, a dedicated instrument is not easy to come by. However, you can build this item of test gear yourself in a few minutes, and it certainly won’t break the bank.
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CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor 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.
Using a sharp hobby knife, completely isolate pins 11 and 4 of IC4 from the rest of the circuit by cutting all copper tracks to these pins. On the IC socket, bend out pins 4 and 11 sideways and solder a short wire to each pin. Solder the IC socket in place (at the underside of the board). Connect the wire on socket pin 4 to the positive supply voltage. Connect the wire on socket pin 11 to the negative supply voltage.
Populate the rest of the board as indicated by the component mounting plan.
Please note that sockets IC2, IC3, IC4 and LEDs D1 through D16 have to be fitted at the solder side (underside) of the board. This allows the board to be better mounted in a case.
R1-R8 = 3k?3
R9,R12,R14,R15 = 10k?
R10 = 100k?
R11,R13 = 3k?9
C1 = 10µF 16V radial
C2,C3 = 100nF
D1,D3,D5,D7,D9,D11,D13,D15,D16 = LED, 3mm, yellow, low current
D2,D4,D6,D8,D10,D12,D14 = LED, 3mm, red, low current
IC1 = LF356
2 8-way IC socket
1 14-way IC socket
S1 = double-pole on/off switch
BT1,BT2 = 9-V battery with clip-on connector
Enclosure, Hammond type 1591B
1 wire link
PCB, order code 030386-1