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How to test 2N6027 (SILICON PROGRAMMABLE UNIJUNCTION)
sdancer75:
Hi,
Is there any way to test out of or in the circuit a 2N6027 PUT with a multimeter? In diode mode (off the circuit), I have 0.7V between Gate(+) and Cathode(-).
My problem is that Anode to Cathode is always ON.
Thanks
Ian.M:
Its effectively an anode-gate SCR. With the anode positive, and the cathode negative, it should pass no current until a trigger current >5uA is drawn from the gate. If your DMM's diode check range goes up to several volts you can use that to test it connected to its anode and cathode. It should initially read as open circuit. It can be triggered by briefly connecting a 10K resistor between the gate and the cathode. It should then conduct with a forward voltage of under 1V, and remain conducting until you break the anode or cathode circuit. Due to its high sensitivity, you may need a high value resistor, say 100K, between gate and anode to prevent false triggering during handling.
sdancer75:
--- Quote from: Ian.M on June 12, 2020, 05:56:01 pm ---Its effectively an anode-gate SCR. With the anode positive, and the cathode negative, it should pass no current until a trigger current >5uA is drawn from the gate. If your DMM's diode check range goes up to several volts you can use that to test it connected to its anode and cathode. It should initially read as open circuit. It can be triggered by briefly connecting a 10K resistor between the gate and the cathode. It should then conduct with a forward voltage of under 1V, and remain conducting until you break the anode or cathode circuit. Due to its high sensitivity, you may need a high value resistor, say 100K, between gate and anode to prevent false triggering during handling.
--- End quote ---
Hi, and thank you for your answer.
Here what I did. I used the diode mode with the red probe connected to the anode and black probe connected to the cathode . No conduction.
I connected a 9V battery negative (-) to the cathode and instantly touched the red (+) to the gate. I had conduction (anode-to-cathode) of about ~0.7V.
Question: It supposed the PUT's gate it behaves as a voltage threshold, which means that anode-to-cathode should have more than 9V to conduct in the case as the gate to cathode had already 9V from the battery. That's the theory at least I have read. Am I wrong? So, why it is conducted while the anode-to-cathode had no more than 3-4 volts from the diode test multimeter?
Regards,
Ian.M:
I hope you had a minimum of a 180R series gate resistor to limit the gate current, otherwise you may well have damaged it.
I did say you might need a high value resistor from gate to anode to prevent false triggering.
Operating as a PUJT (rather than as a SCR), it triggers when the anode goes significantly positive (typ. 0.7V) with respect to the gate, while the cathode is negative with respect to the anode. N.B when it triggers, all three terminals internally conduct, so the gate supply *MUST* have enough series resistance to keep the gate current under 50mA.
If still in doubt try the first test circuit on page 3 of its datasheet: http://www.unisonic.com.tw/datasheet/2N6027.pdf
With a 9V supply and a 100nF timing capacitor it should oscillate at approximately 20Hz.
sdancer75:
--- Quote from: Ian.M on June 12, 2020, 06:50:53 pm ---I hope you had a minimum of a 180R series gate resistor to limit the gate current, otherwise you may well have damaged it.
I did say you might need a high value resistor from gate to anode to prevent false triggering.
Operating as a PUJT (rather than as a SCR), it triggers when the anode goes significantly positive (typ. 0.7V) with respect to the gate, while the cathode is negative with respect to the anode. N.B when it triggers, all three terminals internally conduct, so the gate supply *MUST* have enough series resistance to keep the gate current under 50mA.
If still in doubt try the first test circuit on page 3 of its datasheet: http://www.unisonic.com.tw/datasheet/2N6027.pdf
With a 9V supply and a 100nF timing capacitor it should oscillate at approximately 20Hz.
--- End quote ---
Ok, I tested the following schematic but the LED stays always ON instead of blinking.
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