2 transistors and AC?

Since the Triac (and Diac?) do this job but I'm wondering how regular pnp / npn would do the job.

A negative would switch on the pnp a positive the npn allowing the negative and positive to flow.... could it used to be a switch for AC? or better to stick with something like a TRIAC? it would obviously be for fun (some people don't think people do that on here....)

In theory, you could use an NPN transistor in series with a PNP transistor to switch AC. In practice, there are a few issues to consider:

  • If you are talking about switching AC mains, you would need high voltage transistors

  • You would need to provide base current of around 1/20 of the collector current you want to switch. Where would you get the power from? With a triac, you only need to provide gate current at the start of a half-cycle, and with (say) 10mA gate current you can switch several amps. So it is a lot easier to provide gate current for a triac than it is to provide base current for BJTs in this situation.

I guess in theory you could provide the base current via a transformer and rectifier. Many years ago (before we had opto triacs), the standard way of firing a triac from isolated electronic circuitry was to send short gate pulses through a pulse transformer.

just low voltage, i never mess with anything over 15v ever..... maybe 24vd oooo lol

but yeah, just to switch AC similar to a triac... two transistors you think would do the job?