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I was given to simulate the circuit in the lab. The picture of the circuit from the manual is given below. Diagram from the manual.

I made the same circuit in LTspice. Implementation in LTspice

The problem is that I do not get the expected output as you can see here. Output I was supposed to get a chopped-off sine waveform. Instead, I get this sine waveform which is in the mV range(peak to peak). What am I doing wrong here? Please help me.

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    \$\begingroup\$ There is always zero gate current into U2 in your circuit. \$\endgroup\$
    – Andy aka
    Commented Sep 12, 2022 at 13:18
  • \$\begingroup\$ How to solve this issue? The given manual doesn't specify this. Also, the course tutor started the lab before teaching the theories. Please, help. \$\endgroup\$
    – Rajiv Das
    Commented Sep 12, 2022 at 13:43
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    \$\begingroup\$ As drawn, zero current can flow into the gate. Hint: V1 and V2 are completely isolated in LTspice - but is this the case in reality? \$\endgroup\$
    – rdtsc
    Commented Sep 12, 2022 at 13:52
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    \$\begingroup\$ Current needs a circuit to flow through. \$\endgroup\$
    – Andy aka
    Commented Sep 12, 2022 at 13:52
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    \$\begingroup\$ The circuit from the manual is not working, so your simulation is correct. \$\endgroup\$
    – Jens
    Commented Sep 12, 2022 at 19:25

1 Answer 1

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Generally, diac is supplied with main voltage.

Here an example of "firing" an SCR with such topology (Diac, R-C).

enter image description here

With a battery, it would be a "little" different, if wired correctly ...
Note also that a minimum value resistor is needed ... for safety of devices.

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