Switching 2 MOSFETs with single signal [closed]

Can some point me in the right direction by giving some search words, please?

Problem: I have a TTL signal at 100 Hz. I wanted to switch 2 MOSFETs alternately. Meaning:

pulse 1 = mosfet 1
pulse 2 = mosfet 2
pulse 3 = mosfet 1
pulse 4 = mosfet 2
etc...

• A very warm welcome to the site. Unfortunately, your description is ambiguous i.e. it could mean several different things. Do you mean that pulse 1 turns MOSFET 1 on and leaves it on until pulse 2? Or mean that pulse 1 should switch MOSFET 1 while the pulse is high? Next thing: there's no voltages or anything to go by. You've said 'TTL' so 5 V, right? Remember, if you add detail, please don't post it in reply comments - edit your question and rewrite it to add the detail. The better the quality of your question, the better the quality of the answers it can attract. Thanks. Commented Jun 9, 2023 at 19:03
• I do not think, that this question is missing details required to help the creator. It is just a lack of experience of the creator. Just downvoting for that reason is not really nice. It is kinde obvious, what the creator wants to achieve. If not he can correct us. Please be more welcoming. Commented Jun 21, 2023 at 15:29

Read up on flip-flop toggle circuits. You can use a single JK type or even a simple D-flip-flop. The Q outputs are always inverse of each other, so driving the MOSFET gates from each of the Q outputs will give you alternating on/off signals you could use, the MOSFETs then drive whatever else you need, (like LEDs, etc.).

Here is just one example using a JK flip-flop:

• Thank you very much for your help
– Ravi
Commented Jun 10, 2023 at 4:45

Well, this is possible quite easily, but you need some additional control circuitry:

A 1 bit counter. This means, that (either on the rising or falling) edge of the pulse the counter counts up by one. As it only has 1 bit it switches between 1 and 0. All you need now is an and gate. Now compare the pulse signal and the output of the counter to alternate, which Mosfet to turn on.

Mosfet 1 turns on, if Counter and Pulse are both on (1). Mosfet 2 turns on, if Counter is 0 and Pulse is 1. To achieve this, you need to invert the signal of the counter for the second mosfet.

A single 1 bit counter can be done using a CD4013 (only 1 circuit of this chip required). Another search term you might require is a D Flip FLop.

To invert a signal, a simple BC847A/B/C or 547A/B/C can be used. Just 1kOhm on the base and 1kOhm on the collector connected to Vsupply. With 1kOhm on the base the responsivenes will be bad for turning off (bas saturation), but for 100Hz this is plenty.

And last step might be, to amplifiy the signal for the mosfets, if the logic level output of your circuit is to low to fully turn them on.

But as you want to half 100Hz specifically it sounds like a power inverter circuit attempt. Just do not do it. With this lack of experience you will blow the fets for sure. Building an inverter, that does not destroy itself and a wide variety of different appliences is very, very difficult. I have done a lot, but I still fear such circuits, as they get very complicated, large and expensive fast, just to be "okay enough". But yeah, this is how you can do it.

To avoid all this hazzle and to just get an alternating signal (2 outputs), just use a TL494, as you can adjust the pulse duration of both alternating outputs to more closely resemble a sine wave (it still is a horrible square wave, but voltage RMS wise it is much closer to the real deal). You can find TL494 as a model for LTspice and play around with this software to find the best values to avoid blowing up a lot of the components. You can also simulate the Flip-Flop of course. It is up to you.

• Thank you very much for your help
– Ravi
Commented Jun 10, 2023 at 4:45